I don't cheat. I play survival vanilla. Except when I'm performing admin tasks, I don't even use teleport. My bank in the Mall is using my regular DCD balance, which I earn from my hourly payments, just like any player. My shop frequently drains my DCDs to under 200, at which point you can't sell any more to it. If the sell shop is emptied by a player, you can't buy any more from it.
The reason I'm attempting to regulate the price of diamonds this way is to keep the value of elytra high. Ren has decided that elytra are an end game item, and should not be easy to obtain. So, the rule is that they cost no less than 200 diamonds. All I'm doing is making this mean at least 40,000 DCDs, after we noticed that the price of diamonds in the mall was getting lower.
Anybody can do what I did, the way I did it. The fact that I'm an admin has no bearing on it. If you want to compete with my bank, feel free. You could bring the price down, especially if you're richer than me - which you could easily be if you have more diamonds than me.
By the way, this isn't "the admin account," it's my own Minecraft account. It's my only Minecraft account. I've had it since long before I came to Dogcraft, and I'll have it long after I leave. It doesn't belong to the server.