What kind of contract are we talking about based on recent years/examples? I'm simply not familiar with the NBA enough to know.
Last year, CJ Elleby was drafted by Portland 46th overall - 16th in the 2nd round (halfway through). He signed a 2 year / $2,416,291 - all of it guaranteed. Two foreign players drafted ahead of him in the round did not sign (drafted for their rights). Two American players drafted above him in the round did not get any guarantee. The other 12 players drafted ahead of him signed more lucrative contracts with guaranteed money. Most drafted after him did not receive contracts with guaranteed money.
Obviously, if Preston can get that kind of money, he's most likely gone - and no one would fault him. But needs to be assured to be drafted by the midpoint of the 2nd round to make it worthwhile. Have not seen him in top 46, so he has to catch someone's eye. But as they say, only need one to want you. Agree with most, he is simply taking advantage of the process at this point... but who knows.