Hiding drugs in the coating of sheets is not an example of money laundering.
Homogeneous goods in plentiful supply that are catalogued do not lend themselves very well for laundering money. Price estimates for art reflect what "experts" think someone will pay, based on what was paid in the past, and often a very distant one, and what not that piece has done over time. Paying 100 million for a Van Gogh that "experts" think will make 35 million is not suspicious. Paying 750,000 for a house that was bought for 600,000 may not be suspicious. Having thousands of buyers that pay 50 times market and 5 times catalogue, when substitutes are available at ordinary prices, is suspicious. Also, one customer buying many stamps and overpaying in such a way is easy to identify and investigate.
We, frequently, get people who sign on because granddad had an old stamp worth a penny they saw listed for hundreds by a dreamer. They ignore that hundred similar stamps are listed for a penny. When we tell them the listing is nonsense, we never hear from them again. Some get angry with us, others keep silent. But they never post again. Some list their stamps at an absurd price and never sell.
If you want to see how these dreamers and frauds work, search the forum for Jujustamps.
Look on Etsy, where it is even worse than on
ebay.