You Nerf Money by instituting a tax like that, it is going to piss everyone off, and no one will want to use Meebles anymore, and we wont have to worry about the economy anymore, there wont be one.
All the shops will go up in cost, and no one will want to buy.
And it would be even harder for new players to make money.
Can you imagine if you went to the store to buy some milk, and it was 50% - 75% more?