michael jackson thriller album 78 record. What would it be worth

Are you buying one, or do you have one for sale? Because its worth to you will range depending on your status.
If you have one for sale, I'm afraid you've missed your window of opportunity for making a lot of money with it. Michael Jackson albums, particularly Thriller, were going for as much as $100-$200 right after he died. However, there were so many of them on the market and that, combined with the natural decreasing of interest concerning Michael Jackson's albums, caused the price to go back down.
However, that means that if you want to buy one, you're in luck. They really aren't very much, and if you still have a turntable to play it on, you can once again enjoy the iconic sounds of the 1980s, since this album was made in 1982.
If you want one that is brand new, this LP was remastered in just 2008, and many  major retailers such as Best Buy and WalMart also offer the LP along with their CD selections. Those run approximately $30. However, the old one can be found at places like eBay and http://www.half.com for between $5 and $10, which is all you'll get if you have one you are trying to sell.