We had a high touch service for B2B installation: we charged clients for consulting (business analysis) to configure and integrate our system.
The cost to clients for the consulting was approx 1 year of our SaaS fees. The up front consulting helped heaps with our cashflow, but it also significantly limited our growth rate.
But it worked for us at the time (mid 2000's).
Definitely hard to avoid over-customisation of software for one client: but you need to avoid that problem with any software product servicing multiple clients.
Previous company with a similar product depended too heavily upon ongoing consulting fees and that caused a variety of troubles for that business.