I would say your auction is going extremely well. 21K so far. In the real world, businesses that are approached for acquisition are generally offered 2-2.5x yearly revenue, depending on the type of business (this is a professional services example, for which I am familiar with).
It is a different situation when you are actively trying to sell your business, which gives you a weaker position since you are eager to sell. Overall, it is quite interesting to see what the final value placed on your site will be. 6 months revenue seems a fair bottom-line price.