First is to open up one of the cushions and see if the color bleeds all the way through, meaning its dyed and not just corrected grain leather with heavy coats of pigments. Leather must breath also for it to be comfortable, so should have a nice soft supple feel.

you need to order swatches from Costco and see and feel the leather. I got many leather swatches from Costco.com and most of them are heavily processed (vinyl or rubber like). but few of them look and feel good. so it depends on which brands from costco you're looking for

Nice leather won't be of any use if it's on a poorly made frame. Glued and stapled isn't enough for durability. It should be doweled and screwed and blocked in the corners.

Check out Wellington's sale and "auction" pages. I've bought 2 of their Distinction sofas and a recliner that way-very good quality at nearly half price. You might need to wait till you see a leather or style that you like but it's worth it. My experience was that the auction didn't actually work like you'd expect-I didn't have to wait till the end to purchase-that it consisted of discontinued or end of dye lot leather and item would be made to order. Incidentally, the 3 pieces I bought were 3 different colors but all matched what I saw on my monitor.

Here is a link that might be useful: Wellington's