Hope I've got the right section!

Quick details:

I'm a poor MA student waiting on my visa from UKBA (It's been 13 days). I need to be in the U.K. on the 18th, but haven't booked my flight.

Right now I can get the direct AA 173/174, round-trip for about $1100. It's a bit higher than what I'm normally accustomed to paying, but considering I'm at the two week mark, should I book this?

Is it most likely that fares will go up now that we've passed the two week mark?

...or should I be careful and wait for the student visa?

What would you do?