Update: I had no idea that Ebay had done this or that Gellman had posted his article about it until after I posted this. I was actually thinking of this article* yesterday and didn't get around to it until after I made dinner.
Regardless of resealing and searched wax, which should be seriously considered even if the pack is GIA certified, vintage wax is s suckers bet. There seem to be some rare exceptions. Possibly 63 Fleer Baseball, in other words small sets with cards that sell for substantially more than the cost of a pack or in the aggregate the cards will come close to the cost even if you pull mostly commons.
For my hypothesis I will use common 70's and 80's wax boxes.
Consider the following:
1976 Topps Football.
Single cards: Obviously the card to get is the Walter Payton Rookie. A PSA 7.0 - 8 runs 120-200. PSA 9's run substantially more. Jack Lambert $40 and a gaggle of others $7-$30 graded. Raw substantially less.
The Set: $200-$300
Sealed Packs: Recently on the Bay a Rack box went for $3,650 and a wax box went for $1082.
I get it that if you buy a sealed box you are looking for PSA 9's and 10's but good lord that is a hell of a bet. In the wax you are getting 1 Payton and in the Rack 2-3 maybe.
1983 Topps Baseball:
Singles: The big 3, Gwynn, Boggs, and Sandberg. Three HOF's. PSA 8's can be had for $10, $10, and $6-$10 respectively. Others can be had for $2-5.
The Set: $20-$30
Boxes: Wax As Low as $50. Cello: $76-90
Again, you can gamble on PSA 9's and 10's of the Big 3. Remember though, each box has 540 cards in it and the set is 792. So its possible you might get 1, 2, 3 or none of them.
Singles: Mattingly, PSA 8 $15-$40, the rest are $10-$20 cards max.
Sets: Factory Sets $80-$100
Again, you can buy a factory set or the graded stars for much less than a box.
1982 Topps Baseball:
Singles: Ripken PSA 8 $25 shipped max
Set: $40, Factory sets seem to be $299. Never seen one before.
Boxes: Cello $75 - $120, Wax $75-$95
1981 Topps FB, 1984 Topps FB, 1986 Topps FB have similar differences in price as the 76 Topps Football.
I get that its fun to bust the wax, but with one card per set that is worth anything it is a terrible "investment" i.e. gamble. At least with newer sets there are tons of high dollar cards. I have considered buying a Cello box of early 80's wax just for fun. Some can be had for $2-$4 a pack, so not all that expensive, but not a smart buy either.
*Nothing I write can be considered an actual article.