Walmart offers the Hangman Products No-Stud TV Hanger for 26" to 55" HDTVs for $20.85. Opt for in-store pickup to cut that to $18.03. (Amazon has it for cents more with free shipping for Prime members.) That's $22 off and the best price we could find. It holds up to 80 lbs. and doesn't require any studs, anchors, or screws.

Note: Walmart indicates this mount holds TVs up to 48", but the manufacturer website specifies 55".