Crap Idea and not good .
This has been discussed so often here!
https://bitcointalk.org/index.php?topic=5030366.msg45810953#msg45810953
Buying merit or normal ranks is like buying yourself a bunch of trophies to put on your shelf. It's stupid, and it's an insult to everyone who achieved it legitimately. I can't see ever doing that. I don't particularly mind letting people pay for some of the privileges of these things, such as with copper membership, but it should be a parallel system.
Copper membership is good. Now, if you want to participate in signature campaigns, you can either pay the $10-$20 for copper membership or accomplish the herculean task of making one good post. I don't think that it's unreasonable in either case.
If people are making good posts but are still struggling to get merit, then that's a problem with the merit system and should be fixed on my end. Demanding money in order to bypass a broken system would be really bad. But AFAICT the merit system actually is reasonably effective at identifying good posters.