Hello and thank you for your question.
Actually we tie our pricing for professional services to the user tiers just as with the licenses. The logic behind that is that we offer a guaranteed fixed price. Doing a project in a 2k employee company is way more work than doing the same project for 50 people. The smaller company needs less meetings, less organization and less communication.
If you dislike the fixed price we do offer contracts based on time and materials where you only pay for what you actually consume. Is the more interesting for you?
The guaranteed prices are definitely bound to the user tiers. But you're not forced into buying services at all. You can use our all public documentation of the technology, installation, configuration: https://seibert.biz/diylinchpin
And even carrying out project is documented there: http://seibert.biz/linchpinproject
If you have further questions, please let us know.