bitfury miners and price changes on block erupters

[sr7542]

I signed up to the forum because I am interested in mining bitcoin. I was about to buy some usb block erupters last month for about 12.00 each and it seems like the price everywhere has went up to about $25.00 each why has the price increased? In addition I am also seeking some input as to the difference between the redfury and the bluefury erupters and what there respective costs are in USD.

Thanks