That is most likely because it is not something that happens very often. It only makes sense to take a PG year for draft or academic purposes and many can argue those points. A kid who is struggling to get offers into his senior year of HS is still going to struggle to get offers the following summer as well. Does it make sense to pay for another year of HS to get an offer from a weak D3 school or a JUCO? Probably not.
I can guarantee you that the guys who were drafted out of IMG are not paying 80k a year. 10 maybe and that is most likely a big stretch.