They have to have a lot of less than $10 value decks to make a profit.
This is only true if the current value of these decks is what they paid to acquire them. I suspect that in most cases, certainly the case for their own decks, they paid significantly less than what they are worth now. As long as they acquired most of these decks for less than $10, they are still making a profit. Just not nearly as much as they could.
When figuring how much profit they gain from this deal, you have to also consider how many people will be making a purchase. I'm sure a majority of you guys know more about business and economics than I do, but I have to think that while raising the price will gain more revenue per deck, you'd also be lowering the number of buyers. For example, I bought a brick of these mystery decks last year when they were only seven dollars, but due to the price increase I won't be buying any this time round. And from what I'm hearing, several others are in the same boat.
Now that may be partly attributed to the results we got last year (I got four of the same deck I already had and hated) but I think it'd be ludicrous to say that the price increase has nothing to do with it.
Just a thought that occurred to me and I didn't see anyone else mention it. Hopefully I got it across well enough.