Walmart offers the Spalding NBA Slam Jam Over-the-Door Mini Basketball Hoop, model no. 56099, for $21.98. (Amazon charges the same with free shipping for Prime members, although it is temporarily out of stock.) Opt for in-store pickup to dodge the $4.97 shipping charge. That's the lowest price we could find by $6. It features a polycarbonate backboard, breakaway rim, and 5" Spalding rubber basketball.