selling or buying merit is not against the rules,there will always be people who try to abuse ANY system in place
the thing is,they cannot just get away with it easily
if their posts are rubbish and they get 5-50 merits for an obviously spam post (or a "special" merit magnet topics as I call them)
the rules also do not prohibit for a D1-D2 trust member to waste their efforts by red tagging

don't know where the 28$ figure is coming from,but that is crazy
I think that it is impossible for the admin and staff to catch all members involved with buying and selling of accounts or merits here. Only thing we can do is taking strict against spam posters. There should be clear guidelines like a member making a particular number of low quality posts will get temporary ban and so. All the members here will have to contribute their part in this by submitting correct reports using the report to moderator option. That "report to moderator" options should carry some rewards like merits for accurate submissions.