Best price I've seen is $49 at DealExtreme (free shipping), but it's been sold out for months. Next best would be $75 at SIG Electronics (+$9.99 shipping) that I know of. Probably best waiting a bit if you can though, a new wireless N version is coming out at the current price point, so the G adapters will be getting a price drop soon at retail.
But yeah, other methods like using a router, laptop etc. will always be the cheapest way to go about doing it.