I think what MLB picks up is a fraction of what players spend. The supporter housing (or grouping players into a 6-8 person dorm like setting happens a lot. They are making a better effort with food, but it is still not complete. And then training. Not sure there is offseason training paid for outside periods like instructional league. There are lots of holes.
I actually don't think lots of players would get $100K in my higher bonus system. But some would, and if money was a barrier towards playing professionally, it would just be a smaller barrier. MLB risks getting too selective with their player pool and pushing prospects to other sports or into quitting altogether. They are perfectly happy to not have that short season minor league level. Do we really think as many players will make the majors undrafted as did players previously beyond the 20th round?
I understand this happens because MLB wants to save money and these players have no seat at the negotiating table. That doesn't make it right though.