Buy the music, not the live performance. A live performance is usually suboptimal because the audience is noisy, the venue's acoustics aren't wonderful, the performers have done the same sets for the last three weeks, and you have to make a significant effort dealing with transportation and the like.

Just buy the music. Cut ticketmaster out, cut live nation's venues out, and listen to a great performance with good acoustics in the comfort of your own home as often as you wish. For much less money.