I'm in the middle of recruiting and had cut 2 players, thinking it would add quite a bit to my budget, like GD. Whoops! Now patience is my best friend but need some help in 2 areas.  1. How hard is it to know a SIM off of a recruit?  and  2. How expensive is it to bring a DI player down on the final day of recruiting?

Thanks for any help in advance!

Look at the FSS for the SIM player. At the bottom of the page is an update. If is says things like  "sold" or "very tight", you have almost no chance of wrestling him away from SIM.   If you have a chance, just keep spending money until you get him.  You could spend several thousand dollars, depending on distance and how receptive the player is to you.

As for bringing down a D1 player on the last day of recruiting,.... most of them will have dropped naturally to you by 8 a.m. or 11 a.m.  You won't have to pull them down.  But, if you want to get them earlier, it may require 10-20 scouting visits, a scholarship offer, and possibly a home visit. 
 You should call them first, to make sure they're even interested in your school.