Chaaral,
Just visited a Walmart Supercenter today, and the variety of costumes they've put out is endless. And price is ok, not so high as in earlier Walmart branch I saw. For small kids also they have pirate costume, bunny dress, spiderman costume etc. for $35. There was also a few witch costumes for just $10, but quality was rather poor. For girls princess frocks starting from $28 but colors are too gaudy, Better ones like Tinkerbell, Snowhite are $35 + . More elaborate ones like Red Indian, Scarecrow, Commando, Ball gown , Zombie etc. [ Very scary to look at .

.] are from $45 & above. But I think in US will be much cheaper than here.