Oddly enough, it turns out that eBay has helped reduce the amount of tomb raiding. This is because there has apparently never been that much money in it for the actual tomb raiders looking for artifacts: the high cost of artifacts has to do with middlemen: fences, transport, bribes, authenticators, etc.
So it’s cheaper (and safer) to get into the high quality knock-off market and build cheap fakes to sell on eBay. This means that collectors can get high quality versions of the artifacts and don’t need the actual artifact itself, lowering the price of the original artifact on the market. As this price lowers itself, grave robbers are less likely to incur the costs and risks for a shrinking profit margin.