If you have a 360, go to Best Buy and do the 360 Trade Up thing. You get an extra $50 coupon towards the One, on top of the trade value of the console. It ends Saturday though, not sure when you get paid.
I got my One near the launch, and surprisingly my fiancee offered to pay half of it o.o I guess I had managed to sell it to her as a media thing for the living room, but she was also interested in a handful of games.