I don't know how other teams do it, but it only seems right to give these guys a few thousand bucks for their trouble. Agree, that it's chump change for an NFL team. If it gets you better UDFA's that's fine with me. Plus you are asking guys fresh out of college with likely little to no money to pack up and move to a new city to train and maybe stay for 3-4 months and pay rent somewhere. Seems fair to give them enough money to live on for that time.
Plus, TT seems to keep 1-2 WRs on the PS every year. Highly likely one of these guys will stay on. There is some talent there.