We tripped over the concept of Gimahhot, which is quite an interesting B2C consumer-empowering shopping tool. Prices for a unique product, sold by several merchants, are determined by the supply and demand and the price evolution graph demonstrates the development, similar to the price history of Twenga.
However the difference is that the consumer can decide whether to buy the product at the current price or request a reduction from the merchant. This request, valid for a time specified by the shopper, is sent to the different merchants, selling this product, and the merchant can decide whether they are willing to accept and match the request or not. It is an interesting concept that the individual consumer can approach the merchant and express his intent or willingness of buying the product at a cheaper price.

(Source:
Gimahhot)