It's a good question -- the difference between price and value. Many people deny there is any difference, but I think there is. Was the price of gold at $800 in 1980 the true value, or was it the $400 dollar price or the $252 price? Was the price of NASDAQ stocks at 5,000 in the year 2000 the true value, or was it the 2,000 price a couple of years later? Was the price of houses a few years ago the true value, or is the the current price that might be 25% lower? Were beanie babies really worth $50 just because others might pay that much? In each case, the person buying at the high price probably thought they were paying fair value because that's what everyone else was paying at the time even though they were paying more than just about anybody had ever paid before. But sometimes price is not equal to value and buyers should have some way to determine for themselves what coins were worth in the past, what they are currently worth, and what they are likely to be worth in the future unless completing the collection is more important than the price paid. I admit this isn't easy and sometimes the right answer might be to not buy even though others are buying. If it was, we'd all be rich.
Heritage auction archives, but watch the dates of the sales because it can skew the numbers. If Im too lazy to look at the grey sheet, Ill pull up numismedia and subtract 20-30%. Some PL, DMPL and cameo prices are harder to come up with. Enjoy the hunt!!
The above is actually true. Numismedia, Coin World, PCGS and all the others are just guides and usually say what someone thinks a coin is worth. HOWEVER, a coin is only REALLY worth what someone will pay for it. Yes some coin web site may say a coin is worth xxx but if you can not sell it for that, then that price is useless. Anyone that just wants an idea of a price for a coin could go anywhere but it's when you want to sell it that is important. If no one will pay the prices listed on all the web sites in the world, then they are all wrong.