The main problem here is that houses and software have wildly different marginal costs It is "a" problem, I'll even admit a major one, but it's not the main problem. The main problem is the expectation of continual customization and improvement at the input of the customer. Imagine if houses were built by you contracting with the developer, and after the initial blueprint and plans were agreed to, every two or 4 week…
I work primarily on B2C software, whereas it sounds like you probably work on the B2B software. It seems like consumers tend to mostly accept the platforms as they are whereas businesses feel (perhaps rightfully) entitled to ask for changes in the software they use.
Each have pros and cons, but the marginal cost of B2C software does seem a lot lower than B2B due to the expectations in service.