How much is 2 cent US postage envelope worth?

US Postage stamps from the last 50 or so years are pretty much worth their face value. In large quantities, dealers will buy them for 80 cents on the dollar. You would be better off using them for postage, unless your really need cash. The US has not devalued their stamps since the Civil War, so any stamp issued can be used for postage.

Stamped evelopes are sllightly rarer than postage stamps, but not as many people collect them. They are referred to as "Back of the Book" items as they are listed in the catalogs behind the normal postage stamps. Selling or buying a single stamp is usually not worth the effort to a dealer unless they are of high value. They can make their profits on buying in bulk and selling them in smaller lots.

Older stamps may be worth a bit more. High value stamps, the half dollar and up values, are rarer and worth more. To maximize your profits in stamps, you need to fully identify the stamp, including knowing the catalog number, perferations, watermarks, condition and other factors. If you look it up in the catalog there is a price listed. That price is what a buyer should expect to pay a dealer for the stamp. If you are selling, you should consider yourself lucky if you get half that amount.

Look for special markings. Stamps on envelopes can be worth more, particularly with picture cancellations, First Day Cancellations and special locations.

Find a philatelist and ask for more information!