In my opinion I doubt it is laundering. Money laundering means large amounts of 'illegal' cash needs to be made 'legitimate', he does not have a side business selling drugs, slaves, or gambling. It is highly unlikely he would be generating huge amounts of illegal cash while sitting in prison and all eyes are on him.
I think he is doing a version of 'cooking the books' and this is supported by the fact that he has been establishing a number of stamp companies and then trying to sell them. Additionally, it is not illegal to sell to yourself so he can do this while the heat is on him; the illegal part would only come if he then sells the companies down the road (like once he gets out). He is fine with paying the eBay
fees on selling to himself, this 'cost of doing business' which will be returned many times over if he can find a dupe who believes his cooked books and pays an exponential multiple of what the company is actually worth.
When you own and build a company and work it for years you can some money, but the real money is made when you sell your company. He knows this.