oops, looks like the average was actually 24 silver per 100 gems.
On top of that, currently I can receive 283 gems per gold.. but it looks like I should not do math anymore today, as my calculations from before were either way off or just misinformed.
Forget what I said earlier.
To be honest, one can't really do this (base prices around gems) right now, because the prices are not set yet.
Nobody knows for sure how much a player will have at all times on hand at level 80, after playing for a couple months.
I think it won't be all that much, but I might be wrong.
Still looking for more ideas when it comes to prices guys.