Currently im about 40 hrs in @ lvl 22, though still when i find a object that says "value 1200" i can sell it for maybe 500 if im lucky.
I've tried potions/spells/apparel to improve the prices but still i always get far less than what the supposed value of a certain object is.

Dont get me wrong though.
Even though these prices are far less than the values that they claim to be in my inventory, i have enough cash to buy any training, weapon or tome of my choosing.

So why isnt it that all prices are then just lowered to more realistic values that approach the offers that you get from merchants,
And if you are really good at bartering/speech you can ask for more than the value of the object.
Also, why cant i see the value of a object besides the merchant's offer for a certain object? so atleast you know when a merchant is ripping you off.
For those pricey objects i know the prices by memory, though i cant remember the values of my entire inventory.

Shops in Skyrim follow the same rules that pawn shops follow in real life; Buy low, sell high. After all, they have to make a profit.

true but currently i see marigins that differ 60% from the actual value.
I can see if merchants buy a 1000$ artefact for 900$ from you, while you have to pay 1100$ for it.
but now i get a offer of maybe 400$ if im lucky...

Buy/Sell is based on the Speech skill.

It's all based on your Speech skill (and any perks you've chosen).

You sell for less than you buy for, this is so the merchant can make money and so that you don't get excessively rich too fast.

Put perks in the speech skill and you get closer to the true value. Its always been this way in TES, the higher your speechcraft the closer to the true value you get. Remember you are selling stuff to a guy who will then go on to resell it, of course he is not going to give you full value for it. Just divide your items value by about 3 and you will get a good idea of what you'll get for it at base level.

The only thing that really bothers me about the game is the lack of a buyback feature like Fallout 3 had. I accidentally sell things that I needed then end up losing money buying it back.

Unless a merchant was particularly nice, why would they allow you to sell them stuff and then just give it back to you for the same price? They want to make money.

I am guessing you have zero perks in speech? Basicly at this point you are not bartering at all just agreeing with whatever the guy asks. Same as if you don't expect to be any good at hitting things with an axe if you don't put perks in it

No merchant, in real life, would ever pay even half of what something is worth so that's fairly realistic. In the end it doesn't matter, money is super easy to come by and soon you won't be able to sell any of your loot anyway because it will be worth far more than any merchant has. Or you'll just sell it at a huge loss so it doesn't take up space. All TES games devolve into that conundrum eventually. That's why mercantile was a stupid skill in Oblivion. It just got you to that point faster.

The game is abstracting the bartering process. It assumes that you're going to get the best buy/sell price appropriate to your level of Speechcraft, so you don't have to tinker with price points or sell your loot one item at a time (like in Morrowind).

I thought this is what you see in your plain inventory window. Then when you sell it you see the merchants offer price.

Last time I checked, selling things IRL wasn't as simple as an accidental button press.

The buy-back was also not as much of a buy back as it was a transaction layout, at the end of buying and selling, you'd finalize the transaction.