Totally agree; despite being a mount collector, and having the money to buy one, I can't bring myself to buy it. It's just such a ridiculous amount of gold to fork out for one mount - and it doesn't even fly!
With regards to the gems I kinda feel the first one should be free and reusable - maybe a small fee (~1k) to remove it from the socket; I'd agree that buying a second gem for offspec should still be fairly expensive.
However, I have far more issue with the RNG in even acquiring a weapon to stick the gem into in the first place. Pretty stupid to be able to complete the whole chain and end up with a gem/upgrade you can't even use.