This may sound like a random number I pulled out of my ass, but I ain't lying. I just checked and I have 683332 gold. Yes, almost seven hundred thousand, and I'm at level 44. I have no idea how I've gotten this rich when I haven't even taken any speech perks to invest in merchants or what have you. I think it has happened over time thanks to my meticulate looting and crafting & selling expensive jewelry, enchanted items and potions.
I have every house fully upgraded, so the only thing left for me to buy would be enchanted jewelry (though I can make better ones myself), potions, alchemy ingredients etc. There is no point in buying armor or weapons because my custom-made ones are superior to anything found in the stores. Of course I could buy horses, but I've found them less useful in Skyrim than they were in Oblivion.
I really wish Skyrim had some sort of luxury items or assets for the gold-hoarding players that would cost 100k or more.