Does anyone have a personal fitness trainer? Is it worth the money?

I've had a personal trainer twice (about $600 for 20 sessions) and I don't think it's worth it, unless maybe for the targeted physiological advice, like which correct postures to take, what muscle groups to work on and how.. it's counterproductive to have wrong posture, like say, bending onto your kneecaps rather than your calves, risking damaging them.. A personal trainer mostly helps with motivation too, to get you quickly to a point where you want to be.

Though, I find - for myself - that if I just want to build muscle properly, I might as well go online and do my own research. As for the motivation, I'll bring it up myself.