I should first say the cheap bikes at Walmart, Cosco, Target are cheap not because of the frame. They are because the components they use are cheap. The front derailleur, back derailleur, bottom bracket, brakes, and shifters are all crap. So if you go for a bike like that you are sure to be disappointed in the poor bike build and shotie, half ass work the guy does putting it together. Everyone recommends taking one of those bikes to a bike shop immediately after you purchase it. So, now your 200 hundred dollar bike is 250. Three months later your buying another set of components. Now your 250 bike is 400. You should have spent 400 hun at the bike shop and got free service for the lifetime of the bike.
Here are a few 200- 300-400 dollar MTB's. If you go super low end, I can guarantee you will be fixing stuff within the first 3 months of owning the bike. Now is the time to buy last years model for next to nothing.
http://www.performancebike.com/bikes/CatalogSearchResultView?catalogId=10551&storeId=10052&langId=-1&sortBy=offerprice%2f%2f1&searchType=categoryId&searchTerm=&beginIndex=0&pageSize=16&ipState=c0%3di%253A1%253B3%253Biphrase%2bbundle%2btaxonomy%2bid%2bfrom%2broot%253B400308%253B%253A400308%253B1%252C1%253B0%26q%3d16%26a1%3diphrase%2bbundle%2btaxonomy%252F%252Fv%253A0%26a0%3diphrase%2brelevance%252F%252Fv%253A0%26i%3dsitemap%2bid%26k0.0%3d400308%26qt%3d1255389470%26qid%3dqo0cfdfDhd1xc%26vid%3dvUiDaSeKEjHSP%26ioe%3dUTF-8%26s2%3dsitemap%2bid%252F%252F1%26qtid%3dqo0cfdfDhd1xc%26s1%3diphrase%2brelevance%252F%252F0%26rid%3drIOsH4fBaFWfy%26s0%3dDollar%2bRank%252F%252F1%26t%3d0%26m0%3diphrase%2bbundle%2bid%26mcmode%3dtest&cn1=&categoryId=400308