Okay budget gurus. Where should I go to buy good quality kids' bikes? My kids could both use a new one and they seem to need a 20" one. I would love to be able to get them something like a mountain bike that would last well. They have lots of shiny new ones at Walmart but I don't trust the quality. I thought I would take them to a used bike shop and get something good there but they seem to still want hundreds of $$ for the used ones! Is there some hidden resource I'm missing where I could get nice ones for $50-75 each?