> But it makes sense to put the common easy cases and then ask for contact in the rest. Which is probably the path we take as it will save us some time.

That would indeed be great.

Also, if complex decision tree is your real objection, then consider putting a price range. "Depending on X, Y and other factors, the price ranges from A for minimal deployment low on Z, to B for large-scale solutions.". Or something like that.

Exact prices are always the best, but estimates for typical cases and a price range are second-best. It lets a potential user decide whether to even bother checking your service out.