As a Canadian mint collector, I don't even know when or why I bought this, but can someone please tell me the current value of a 50 stamp mint sheet of the 20 cent face value State Birds and Flowers stamps with a US Postal Service copyright of 1981 on it. Appears I paid $24.95 for it at the time.
Scott #2002b, Pane of 50 US State Birds and Flowers issued 04/14/1982 has a current "catalog" value of $27.50 (VF, MNH). Of course, the stamps are quite common (666,950,000 stamps were produced) and therefore they typically go for only a fraction of catalog value on the secondary market.
There is a minor variety, known as Scott #2002Ac, which is an 11.25 x 11 perf variety (as compared to the 2002a which was perf 10.5 x 11.25) but even with that variety, there's only about a 10% premium in catalog value.
Still a very pretty stamp issue that many collectors enjoy.
Value is relative. Scott catalog value will show you what you might be prepared to pay directly to a stamp dealer.
On the other hand, you can check completed listings on eBay to see what some collectors are paying at auction.
The Scott numbers for the sheet you have look something like xxxx-yyyy. Take the xxxx and do a search on eBay for active listings. Then look at the far left side of the web page where you will find a gray column with various boxes you can check. One of the choices in that gray column is "Completed Listings." Check that box and the search will done with no further clicks required.