"The big exercise trend is going to be group fitness classes. A spin class is considerably less money than paying for a personal trainer."
Source [1] and Source [2]
Links:
[1] http://www.nbc.com/The_Biggest_Loser/photos/#cat=1071
[2] http://tracyandersonmethoddvd.amazonwebstore.com/Tracy-Anderson-Method-Presents-Dance-Cardio/M/B001F2JVSO.htm