Some people consider this a cheat, but I use Creeper for situations like this. If you're unfamiliar with him, he is a domesticated scamp who lives in the large manor in Caldera across from the nord armorer. He has 5,000 gold and pays full price for weapons, armor, and potions. He won't buy ingredients or books or just about anything else. He does, however, buy dwemer stuff, including the coins, which is one of the best ways to easily get your gold back by the barter system, because there are so many coins in the game, and they are all worth 50 gold each. So, when you've sold him a couple of hundred, you can just do the math in your head, buy back the number you need to balance out the transaction, then sell them back in sets of 100 each.
There is also a mudcrab that you can interact with who functions just like creeper, but has 10,000 gold. Only problem with him is that he lives on an island to the East of Vivec, but is not really close to anything else, so you have to constantly search him out, or permanently keep a 'mark' spell at his location, limiting the use of the spell, so I just don't bother with him. Besides, half of the time I kill him by accident without thinking about it when I'm down his way.