How to make the most of a sports trading card investment?

A friend has been collecting trading cards from all major North American sports leagues for the last 20 years. Most of the purchases were made between 1990 and 2000. These were bulk purchases, several boxes at a time (mostly special edition boxes), and to this date none of them have been opened and they have been well stored. Easily over 200,000 cards in total. Would it be best to open them up, see what treasures are inside and trade them online? Or would it be better to seek out someone who wants to buy them all in one shot, without knowing what's inside?

How to make the most of a sports trading card investment?
Ok...there is no pat answer, what he has could be garbage or good stuff. First and foremost, have him purchase a magazine called 'Tuff Stuff' ($6 on newsstand). Look for ADS (nothing more) that state "I want to buy in bulk - boxes or cases". It will give basic idea of prices. Some might sell for $25 box, majority $12-30. Card market off since 1990, as over 300 businesses were selling them. In 1987, there were only 4 major card sellers. If he checks with a local source/flea market/etc. cards are worth 40% of retail price they offer. Best to sell in bulk, as more time spent opening each than what they're actually worth. Examples: 1 card per 100 will be worth $1...1 card per 1000 will be worth $4...only 2 or 3 will be worth anything, with less than 5 cards worth $20-30 in his 200,000+ cards. Most cards would sell 20 for a penny. A lot of sub-sets that might have 10 or less cards will have more value than a complete set of 800-900 cards. When he does decide to sell, start high on price and then he will find out just what he might receive in the area he's selling. They will accept offer knowing they're getting a good deal, or balk at the price being too high. ANYway...if he has a list of what he has, could give a much better idea whether they are worth $5 or $20. (email me) More than happy to help you out. Consensus says he will be lucky to break even, but more information needed to truly know. Hope this helped a little and didn't confuse you/him more. No charge, btw...