Well they are only expensive if you buy them. I personally have never bought a dragon you needed gems for. I have only purchased gems twice, once to speed up me getting the EBI and the second to upgrade my hibernation cave, and I only did that because I ran out of room before I had enough 'free' gems.
I just think because we have the potential to get up to 9 free gems a day (6 from friends and 3 from the colosseum) having a dragon that produced a gem once a day or every other day, would help people like me who want the upgrades like the breeding caves without feeling they have to buy gems.
GC ID: Steffany_W