There are 3 kinds of express at Universal.
1)The express pass is free just like at Disney. You scan your ticket in the express pass machine and an express pass is printed up. The only difference between the express at Universal and fast pass at Disney is you get to choose between two different return times. And it is free just like at Disney.
2) The express pass plus used to be a booklet of passes for each ride but now is one card that is scanned at the entrance to each ride. You can ride one time on each ride and you decide when you want to use it. It is not set to a certain time frame. The express pass cost varies from $30-45 depending on the time of the year. You have to purchase one for each person in your group. The express pass is only good at one park so you can buy one for Universal or one for Islands of Adventure. They do have one you can purchase for use at both parks but it costs more.
3) The third type of express is called FOTL (front of the line). You get in by staying onsite at one of the hotels at Universal. It does not cost extra and is a perk for staying onsite. You can use FOTL at both parks and as often as you want (unlike the other passes that you can only use once per ride.) Last summer, for 2 months, they did put some restrictions on the use on re-rides. You could still use FOTL but couldn't re-ride the same ride until after 3:00 PM. After 3:00 you could re-ride to your hearts content. Right now though there are no restricitions for re-rides.