You can get lucky sometimes, but it's hard work trying and can become very tiring after a while. I admire people that buy and sell on ebay (properly I mean, not just with endless suppies of new items) but you'll need to continue a lucky streak. On a related note, your grading of coins is very suspect. All I've seen have been overgraded or have had a higher grade implied. But, that in itself is common on ebay and the real collectors know what they're doing.