Coach, you are not going to find anyone more supportive of DIII than me. A DIII coach made our son one of those few who got drafted. I know how hard he has worked to get 2 other kids a shot...and how hard it is. Maybe scouts do a better job in TX and the other states with SCAC schools but, IMO, getting to sign a professional contract from DIII does not happen "often" whether you are a free agent or a drafted player.
According to the DIII baseball website that started this thread, there have only been 10 free agent signings in the last two years...from all of DIII baseball. Assume you must have been including independent leagues and the like which does increase the numbers, I would agree.
http://odac.bridgewater.edu/div3base/draft.htm