"I picked them up at a thrift store, I paid about $75 for the lot to answer that question and just some of the unused ones that are in an envelope are worth far more than that based on eBays ended auctions in the last month."
Be careful here. What you see on completed
ebay auctions may not be the same stamp that you see in the envelope that came with your collection. Higher value stamps often have lower value versions that, to the neophyte, look like the same thing. Watermarks, perforations, shades of color make a difference even when identifying which specific numbered stamp in the catalogue you have.
And even if you do actually have the same stamp that just sold on
ebay for $30.00, keep in mind (1) sometimes things sell on
ebay for prices way beyond what they are worth--they sell that way to newbies! and (2) even if what sold on
ebay for $30 was worth it at that price and you have the exact same version of that stamp, still, your stamp may have a flaw or two that takes it down from $30.00 to $10 or even $5.00.
So, figuring out just what your particular stamps are worth takes a good bit of effort at first. One solution is to get help from an experienced collector on site, in your town, at a stamp club. I'd suggest consulting a dealer, but bricks-and-mortar stamp shops are nearly entirely gone from the American landscape.
Another solution is to post decent-resolution scans (not photos) of two or three of the stamps you think match stamps that sold for good money on
ebay. People here can't assess condition or do the really tricky identifications completely from scans but often flaws are visible, if the scans are decent, and usually there's someone here who can identify even very tricky cases from scans. Doing that for two or three will begin to give you an idea whether you have anything worth more than the few cents a stamp that the vast majority of stamps in an estate sale or thrift shop album usually are worth.