Am I able to get away with saying market forces? Some economical terminology.
Basically if people don't want to buy, the suppliers just cut back so they won't sell anymore than they have to, so the price remains the same.
And it works the other way, to keep the price the same.
Really if you want to get the better prices you need to look out for when the prices rock up, you buy. When they rock down, better keep the notes in your pocket. If you do buy something during the prices rocking up then there's not really much point selling at that point, you'll just have to wait with it till the price goes down. It always does. Just depends how long it takes.