Lifetime membership on Blockland - $20
Lifetime membership on Roblox - $200/$300
Laughing at how Roblox thinks people will actually buy that - Priceless. 
Meh, that's just for extra's such as ability to sell stuff, create groups, have more than one place up, get specials hats and gear, try out the beta stuff, and have a live chat with the developers for the most expensive one.
But it doesn't give any disadvantages. You can still have unlimited bricks. You can still script as much as you want. And you can still earn money from place visits.
But many people complain that Builder's Club was one of the worst ideas the developers came up with.