Retail for the AirPort Express......both 802.11n versions......was about $100 in the U.S.
Because of continued demand for the product......which was discontinued over 2 years ago....some sellers are now getting up to twice the original retail price or more for refurbished AirPort Express products.
If you need an Express, might be better to buy now as the price will likely continue to increase unless you want to look at used products on Ebay where used Expresses are available at prices that are all over the place.
My experience with Ebay with AirPorts is that if you buy two, one might work.