Why isnt there a site like this
 

Maybe there is and I do not know about it .

I want to buy something so I post on a forum.
I want vendors to compete for my business.
All 100% transparent in the "thread"

If it does not exist some one or maybe me should invent it

Kinda like a reverse groupon but not

We have something similar. On skinme5.com, people can either post what they will do for $5 or they can post what they would pay someone $5 to do for them. So, for example, you need a quick logo done for your business, you can post it on skinme5.com and people can "Apply" for the job. So, if you have more than one person who wants to fulfill it, you make the choice as to which one you want to place the order with.

99designs but based on tendering for jobs?

I was not looking for a fiver clone buddy.

I am talking about shopping. I want a new car type thing.
Large purchases lets say $5k +

No worries. I didn't know what you were looking for exactly. Just offered up an option.

Autotrader.com is probably the closest thing I have seen to what you are looking for.

I am not looking for a car. lol

thanks for the idea. will let you know when it's up.

lol. I've been thinking off an on about that idea for a while now. There are forums like that out there, though, even with people asking for weird niche paysites but I don't think those are extremely popular.

http://techcrunch.com/2012/06/17/ubokia-embeddable/ some one made it

Yeah, it's called a "want ad".

For example :

WANTED :
1967 Ford Mustang for body parts.
No engine OK.
Quote price!

Every one is busy making Tube sites and has no time for real money making ideas.