You can buy individual scenes with money, or buy PPM time or Buy different sized Tickets packs what you can use to buy scenes. A bit of a warning tought the site is quite a mess and quite annoying to navigate and i heard that if you got some problems the support is quite poor, but i havent had too much problems so far. Also if i remember right when i joined in quite many scenes the trailers didint work and sometimes the PPM didint work either so you had to do blind buys sometimes. Also they havent updated new scenes in a while ( Supposed to come soon but it is sineplex so you never know ).
The quality varues, the new evilutionplex is 720p atleast, dont remeber if there was option for 1080p, and the scenes were in mp4 format i think. The old sineplex stuff that has been released on DVD before is DVD quality.
Seems they have lowered their prices a bit since i last joined it. Their Trial offer is pretty cheap and you get 10 tickets with it, so you can test it out and see what you think and if there is some troubles you dont loose that much atleast.
http://legalporno.com/join