$50+, ballpark, depending on which model/features you need. Stick with name brands if possible so you get support you need. Also, make certain you are using dual band 'N' wireless if possible to maximize your performance.
I have a blu-ray player on the 3rd floor of my house, but my wireless modem is on the first floor (only place we can plug it in). The blu-ray player often doesn't receive the wi-fi signal so streaming movies often stop suddenly until a better signal is received. Short of buying a 60' cord that will travel up the stairs and connect the two devices, how can I get a better signal??