What I can say is, "very easily." Blank DVD+Rs and DVD-Rs are available retail for less than 50 cents each if you buy in bulk (100 or so). I'd guess that wholesale bulk prices can't be more than 25 cents for porn companies and probably even less for Hollywood (probably = almost certainly).
Once a DVD has run its course and made back all of it's production costs, returns are almost 100% profit. That's why companies can sell DVDs in the bargain bin for $5 each.
Once production costs are met, a $10 DVD is at least 900% profit (that's allowing for a roughly $1 distribution cost, which is probably excessive).
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