The current Daily Deal for gold (April 24, 2019) is 5000 gold for 450 gems. That is roughly 11 gold per gem.
However if you scroll down to the every-day Gold for Gem deals, you can get 750-2500 gold for 60 gems. Assuming the range is completely random, that is an average of 1625 gold for 60 gems, which ends up being 27 gold per gem. Even if you use the lower bound of 750 gold, that is 12.5 gold per gem, still higher than the Daily Deal!
27 gold per gem vs. 11. What the heck?