That doesn't make anyone rich, it just gives them great positive balances. However, as the ones lower down never actually pay their dues, none of the temples have the required treasuries to hand out to those up top.
And if you want people to buy lots of ranks... good luck. Still, to be successful, you'll need a lot of guild houses, or large guildhouses, so that the max full member count isn't too low. And doing so costs a lot of gold... much more than the rank fees will bring back. All of these constructions, as well, will take your gold, but not modify your balance, always leaving you in the net negatives.
Your mistaking making guilds profitable overall and making it profitable for a one or two people. SA for instance (religions are guilds) could definitely be profitable for leaders because of a lot of donations by a lot of people. Is the guild a gold sink? Yes, but it can still be profitable for a some people.
