I have to agree with the comments here about 100 gems just to remove a lv 4 chip... I can think of much better methods just off the top of my head!

1:
start at lv 3 costs 1 gem to remove. (so people know the penalty starts)
lv 4 --- 10 gems
lv 5 --- 20 gems
lv 6 --- 50 gems
lv 7 and up --- 100 gems

2:
use the same gem cost for removal protection...
sooo if you want to remove a gem it is free but it it will break (a lv 4 becomes 3 * lv 3 gems)
costs of protection is (you get the gem back) 100 gems
or use the costs above for gem protection...