Oblivion did have this. You had to bump up your speechcraft in Oblivion to increase the venders stock in coin. In fact there was two perk investment increases in Oblivion available.

Yup gold ore, totally wasn't iron ore just a minute ago.

In Oblivion it was no point in taking heavy expensive items. In Skyrim you barter, buy crafting materials from an smith and sell him loot.
Note that this also level you speech skill fast. Say you have lots of expensive loot, you buy filled grand soul gems from an merchant and sell back loot. Yes you could use Azura's star and killed mammoths however you have more loot than you need so why not trade it. say sell for 3000 and buy for 2000.

However if you even dabble in crafting you don't need to sell loot. Enchanted iron daggers with banish is worth 1500-2400 gold. giant toe, creep cluster and wheat is worth thousands, salmon roe, chicken egg and wheat might be worth more than 10.000, comparable with legendary dragon items.
The speech skill level level up gain is based on the price of the item, not the money you get.

No need for it, say you loot an dwemer ruin, all the scrap metal are heavy and you want some falmer armor for your collection nothing to sell. Yes you could use the pack mule (Lydia) however if you sneak you might not want an follower.

Zaria cast transmute two times and looks at her iron ore.

Yeah, smithing and alchemy components are why i use the bag of holding mod. I like how in Kingdoms of Amalur crafting componens are are stored in separate inventory, (it doesn't have weight limited inventory, but space limited one) and using that mod makes it work smilarly-ish.

And the assistomatons' inventory is too many clicks away to use them pack mules, unlike in New Vegas. They are hardly useful as meashields either. And their repeated one-liners dont help

Same here.

I admit that I do kind of miss this as well, if only because I loot so much that it takes a while to sell it all.. my characters in Oblivion got rich so quick it was crazy because of the things that I would loot, but I had a mod to help me carry it all with me.

I do have the same mod in Skyrim as well, but I don't loot as much because a lot of things I come across I consider junk except for enchanted items.. which I usually use for my characters armor depending on what enchantment is on them.

I say no thanks to infinite money merchants. I mean maybe the mudcrab merchant could come for a visit on the coast of Skyrim. Im sure he could breathe better since Red Mountain exploded , and he has more money than other merchants. Oh and yeah what everyone else said about Speech , you get discounts , and Allure gives you 10% bonus with merchants of the opposite six and the high end being everyone gets 1k gold more. I dont see the magic in getting filthy stinkin rich where you can buy everything , kinda ruins it for me.