The major ERP vendors do not price based on product or services delivered, but they will just make a price based on your revenue.
The reasoning is that a company in a certain vertical with a certain size will spend x% of revenue on IT, and they want all of that.
ERP platforms are ridiculously hard to customise, and maintainance of customisations across version upgrades is even worse. So they will rightfully advise business operations adapt to the ERP template, rather than the other way around. They know full well in advance you will end up not following that advice as the changes would be enormous and lost functionality as compared to the previous system beyond tolerable from a business point of view, but they also know you will only discover the scale of this after the project has been committed.
Speaking about committing: they will leave no room, basically execution a denial of service to the whole of not just your IT departments but also all your business analyst interactions. Any non ERP transformation project will grind to an absolute halt.
Many of not most of these huge ERP migrations fail. The ERP vendor has been covering there ass from before the contract was even signed, and you will find their real expertise was building an airtight very well documented case showing you, not them, were at fault. These cases are nearly always settled and kept out of the press because neither party wants to lose face.
And you are right about the mother of all lockins if the project should succeed and actualy move into production (which they will try to force long before it is ready). They will leave you no room to ever go back. You'll have to commit even a lott more to leave than you needed to get in.
And as for all those business and IT people now trained on the ERP, wich is part of the project from day 1, good luck holding on to them. Their poaching will be not overtly but discreetly facilitated by the ERP's channel.
First day of first 'course' by the ERP vendor for the ERP transformation team, the opening sentence of the instructor litterally was: "I congratulate you all for being here. Next week after completing this course, walk into your manager's office and demand a 20% pay rise, as you are now worth that".
I myself have turned down very lucrative monetary offers, as the downside of working in those projects, whether at vendor or client side, is that the amount of unhappiness you create and are perpetually surounded by in those positions is just to mindnumbing that at least for me the money does not buy you out of that daily misery. But if you thrive on conflict, you can make some great money there.
I worked on an ERP system for construction/architect firms in the 00s. The company was about 15 people when I joined, 40 when I left.
We consistently delivered migrations, but we hand crafted SQL extraction scripts, with data cleaning, etc. You could fully customize it, branding it with your own logos/colours/custom css, etc. There was just a clause that the "powered by" link had to stay visible.
I can't remember a single failed migration, though we were split into three "teams" each covering a different set of customers, so might have not seen one.
I suppose we were fairly small scale, and maybe those were the days where some serious attention to detail and care of the customer were still possible as generally we were replacing paper based workflows, not trying to migrate existing electronic workflows with huge data volumes.
But it's perfectly possible to do (and we worked with some fairly big companies in the space).
One of the funniest, yet saddest, support calls I remember getting was being asked "What do we do with Sue now, we don't have anything for her to do anymore?".
So it entirely depends on your implementation team I think. It's possible to do it well. But you probably need a very good set of consultants. If your ERP trainer is coming in and immediately setting up conflict with your company, that's definitely not a good sign.
Small scale is definitely another world entirely. My experience was not in the Billion dollar range as the parent, but in 20M+ (probably 50M in today's dollars) project territory.
> So they will rightfully advise business operations adapt to the ERP template, rather than the other way around. They know full well in advance you will end up not following that advice as the changes would be enormous and lost functionality as compared to the previous system
There's an additional catch to that old argument as well. If you actually do what they say, and stick to all the templates. Well guess what, they're all going to change with next update as well and now you need to change all your business processes at the same cadence as they happen to update their software. You still have to adapt to the changes of the system, it's just not the IT departments problem.