Sharing the cost of a trainer makes it affordable to have personalized attention. Plus you won't miss a work out because you won't to waste the money you've already paid on the trainer. Friends waiting for you keeps you accountable to show up (and accountable when out together at restaurants).
Myself and two friends purchased time with a trainer. We opted to meet at a park in the middle of us & exercise "boot camp" style outside since we all belonged to different gyms and lived in different directions. We like it so much that we've just signed up for our 7th month.