A quote for a new system implementation looks precise in an email. Licences: this much. Rollout: this much. Total: a specific number you can drop into the budget. The catch is that this number covers roughly half of what you'll actually spend over the first eighteen months.
This is not an article about vendors cheating you. Most of them don't cheat — they simply quote what they know how to quote, and everything else goes into the "it depends" box. "It depends" doesn't make it into the budget, so it doesn't exist. Until it does, no longer as a plan but as an invoice.
What you actually see in the quote
A standard implementation quote for an SME has three lines: licences (one-off or annual), implementation cost (person-days × rate × defined scope) and something like "post-go-live support" for the first 3–6 months. Everything looks tidy, the vendor can defend it in Excel, the client can approve it at the board.
The problem: this quote answers the question "how much does it cost to spin up the system in the version from the demo". It does not answer the question "how much does it cost to move the company onto it". And the company is not a demo database with 20 customers and 100 products — it is a dozen or more years of history, eight people who work differently from the textbook, and five other systems the new one has to start talking to.
Six categories the quote doesn't include
Nine out of ten implementations we pick up off the floor blew their budget for the same set of reasons. Worth knowing them up front.
- Data migration. The vendor usually assumes you'll deliver "data in a standard format". A standard format doesn't exist — your data exists, in your Excel files, with your local conventions ("tax ID with dashes", "weight as text with the unit"). Someone has to clean and map it. Usually you, because the vendor "doesn't know your industry". Real cost: 60–120 person-days on the client side for a medium-complexity ERP.
- Integrations with what you already have. The bank, the courier, the online shop, KSeF (Poland's mandatory e-invoicing system), the warehouse label printer, the time-clock terminal at the entrance. Each of them is described in the quote as one sentence: "standard integration if API available". In practice "standard" means the vendor has a template that needs to be adapted to your version, your bank, your Comarch Optima configuration. Budget 3–8k PLN per integration, and that is the optimistic version.
- Training and productivity dip. The quote typically includes "2 days of training for key users". Great. In practice, for the first 6–8 weeks after go-live people work 20–30% slower because they are looking for things in a new place, making mistakes and asking questions. This is a cost nobody will invoice you for, but it lands in the company's bottom line. In a 30-person company at 8k PLN/month fully loaded per FTE, that's roughly 40–50k PLN in wages for productivity that didn't happen.
- Running two systems in parallel. Nobody switches off the old system on go-live day. For 1 to 3 months you run on both — last month's invoices have to be issued from the old one, the quarterly report closes in the old one, the customer with a complaint gets handled in whichever system had the original transaction. Someone has to coordinate that. Usually one too-good employee working after hours for those months.
- Modifications for "but we always do it this way". At kick-off everyone agrees to fit into the standard. Three months after go-live it turns out that in your industry a pro forma invoice has to look different, the courier wants parcels labelled your way, and the warehouse manager won't put down the scanner until it behaves like the old one. Each of these is a change request — extra person-days at the vendor's hourly rate, without the implementation discount.
- Licence scaling. The quote priced 25 users at today's price. A year later the vendor raised the list by 12%, two more people joined, someone added an "advanced reporting" module that was "on promotion". The annual licence cost that was supposed to be stable grew by a third.
A concrete example
A 30-person manufacturer of precast concrete elements from Silesia (prefabricated building parts, roughly 45 million PLN annual revenue) rolled out a new ERP in 2024 to replace a system more than a decade old. The vendor's quote: 90k PLN net (3-year licences + implementation, about 45 person-days). Deadline: 4 months. Everything looked good — until the rollout actually started.
The real bill after 14 months, when we took the project over, looked like this:
- Base quote (licences + implementation): 90k PLN
- Data migration (5 years of sales history + master data): additional 32k PLN
- Bank integration (mBank, non-standard format) and KSeF: 18k PLN
- Warehouse system and labelling integration: 24k PLN
- Change requests (12 of them over the year): 41k PLN
- Extended post-go-live support (stretched from 3 to 9 months): 22k PLN
- Overtime for 3 employees who worked "on both systems" for 4 months: about 35k PLN (cost to the company)
Total: 262k PLN, or 2.9× the base quote. Plus 10 months of slippage, and for half a year after go-live the company reported sales late because nobody fully trusted the numbers in the new ERP.
To be fair: this is not 100% the vendor's fault. The client also overestimated its readiness to change ("our people learn fast", "our data is in order", "we don't need modifications"). But if all these items had come up during the offer stage — the decision on the rollout would have looked different.
How to force an honest TCO
You don't have to be an implementation expert to ask questions the vendor has to answer in writing. A few specifics worth putting into the RFP:
- "State the client-side person-days you have assumed for data migration and mapping preparation. Who coordinates it on your side?"
- "List every integration as a separate line item with pricing. Which of these have you already delivered on this system version, and which are you doing for the first time?"
- "How many change requests typically come in during the first 6 months after go-live for a client of our size? What is the hourly rate outside the implementation package?"
- "What annual licence price increase do you assume for the next 3 years? Are you willing to write a cap into the contract?"
- "How many months does the parallel-run period actually take at a client of our size? Who on your side supports the coordination?"
A vendor who honestly answers these five questions will probably offer you a higher price up front. That is the good news — you are buying a plan, not a fantasy. A vendor who brushes them off ("that depends on you") or promises "we don't have those problems" has just disqualified themselves.
What next
Before you approve any quote on a system bigger than a few thousand euros, take a sheet of paper and write down the six categories from this piece. Add a realistic figure for your company next to each (a range is fine). The total you get at the bottom is your real TCO for the first 18 months — not the one in the quote.
If you want an outside look at a quote you've just received and the questions nobody has asked the vendor yet — we do these reviews for SMEs. The first call is free and takes half an hour.
An honest implementation quote is higher. But it is the only one you can keep.