When buying cheap binoculars for astronomical use: be sure to test them on a real star. Many cheap binoculars have optical or alignment errors which are not evident in daytime use, but which become glaringly obvious when you try to focus on a star.
Stop by the store any time after dark on a clear night, and talk the salesman into letting you take a pair outside for star testing. If the salesman balks, offer to leave a driver's license or credit card as collateral. Be sure to test the unit you are planning to buy, not the one they happen to have sitting in the display case (unless you intend to buy the one in the case); don't assume that because the demo unit is aligned, another binocular of the same model will be.
I use a Simmons 10x50, $29.95 on sale at Big 5 sporting goods, and they work quite well for casual astronomy except that I occasionally want a lighter binocular with a wider field of view, When Big 5 advertised a Simmons 8x40 on sale a few months ago, I tested one on a star and found that I could not focus to a sharp point image, nor could the Bushnell 8x40 they offered when I brought back the Simmons, so I passed. (Had I really felt strongly about getting an 8x40, I would have asked to try a few different units of each model in the hope that I might find a good one.)
For more information on binoculars (not just cheap ones), read Jay Freeman's excellent article on Some Advice on Picking an Astronomical Binocular.