if you're willing to fly y, there are around 30 flights available for y400 ($50). as far as specific choices are concerned, i usually try to avoid mu and hu at all costs (though i might make an exception to try an mu 343/345). between fm and ca, i prefer fm, but ca's new 777s are pretty nice.

btw, elong is a pretty crappy site imo. they use bait and switch pricing (so does ctrip, to a much lesser extent, because the listings you see aren't real time) love to tack on fees of their own that set them apart from almost every other ta i've ever dealt with.

i suggest you wait till you get to beijing before buying a ticket; those fares will probably come down a bit between now and april 2 (and will likely hold steady or rise again between the 2nd and the 5th)

edited to add: i just realized that you want to fly sha to pek rather than vv. that's usually a bit more expensive (i often pay close to full fare), but there are still a handful of flights for y450