Immediately following the announcement of Michael Jackson’s death, enterprising individuals began selling memorabilia online to take advantage of the increased demand.

The Better Business Bureau warns that the value of most memorabilia and commemorative items being sold is sentimental, and the currently inflated prices for many items will drop over time.

According to Smartmoney, before Jackson’s death, sellers listed an average 200 to 400 memorabilia items daily on eBay, but by the morning following his death almost 20,000 Michael Jackson-related items and memorabilia were for sale on the auction Web site.

In addition to memorabilia, commemorative items are already being mass produced and sold to fans — including T-shirts and special-edition newspapers and magazines. Because the value of collectibles is largely dependent on how rare an item is, mass-produced commemorative items are not likely to appreciate in value.