The best "toy" that you can find under $10 is PLAYDOUGH!!! Children use their imaginations when they play with it and it can keep them entertained for hours!! We have a big box with different colors of playdough and rolling pins, plastic knives, cookie cutters, etc. All kids love playdough and you can buy it cheaply or make your own!!
http://stealsanddealsforkids.com/2012/05/05/crafts-for-kids/how-to-make-your-own-playdough/