Value' is an elusive concept. There is no obligatory relationship between the price one pays, or has paid, for something and its 'value' The same for profit. Perhaps nothing causes more consternation among beginning collectors than the issue of prices.
Pricing is a little bit like zen and after a while it begins to make sense - sort of.
If you buy only on the basis of price, you will wind up with a cheap collection. In every sense. Maps at the bottom end of the price range will, on the whole, have problems that, as a beginner, you might not recognize. Go to any car dealership and buy only the cheapest used cars on the lot. Yes, some dealers seem to charge more than others by hundreds of percent.