Some chapters may have a delayed payment plan to ease the "pain" of joining although they may have rule that when you pledge, all outstanding monies have to be paid before you "walk down the aisle" or whatever at Initiation..once you are initiated, it may be easier to be approved for a promissory note or whatever.
Yes, GPA is very important. Most chapters have specific rules about studying. For example, let's say that a group has a rule that those below a 3.0 have to do some proctored hours each week..the farther away you are from the 3.0, the more you have to be proctored.
Yes, it's cool to see some famous person and be able to say "that's my sister or brother"..even though you'll never actually meet them. Of course, it's also neat to find out that the person living across the street is your sister or brother".
And it's fun when you "meet" on GC and then actually meet them in real person.