We would love to be able to do that but it would be abused too much it's been suggested many times in the suggestions section if you need reason but trust me, it wouldn't be good....
You are right, already prices have dropped from around the 3.0 - 4.0 price down to around 2.0. I personally think ~1.0 or less is the recommended price to buy resources on the market. I value Haypi$ quite high because of the huge bonus that research gives.