Typically, you wonít get back near what you put into a custom job like that. I would keep them if I were you.
You need to find a person that wants the exact custom work you had done.
Check Gun Broker to see if you can find similar guns that have sold. But a quick look there are lots of RMR Glocks for around $1,000, then there are others people are asking $3,000 for. Be sure to search for ones that have actually sold, not just what they are asking for.
You might get more out of them by parting the guns out selling the slides, RMR, triggers, ect... separately.