If they don't make you a good written offer then they haven't really done anything to stop you from finding something better to do once the novelty of working w

If they don't make you a good written offer then they haven't really done anything to stop you from finding something better to do once the novelty of working with them wears off (which will probably happen really fast the moment you think you've been screwed, true or not). It doesn't sound like they are complete fools, so the only rational explaination is they aren't concerned with you staying or leaving, and neither is their client.