How are copy protection schemes charged?

Sometimes I have copies of both the original CD when a game first came out and a compilation by the company a few years down which also includes the same stuff and extras (usually marketed as a “White Label” one) to get some pesky add-on I missed.

I noticed that in all instances where the original had a copy protection scheme of some sort, a few years later when they repackage and remarket it with its add-ons, etc, the repackaged CD now does not have copy protections.

Presumably, this is because the company has to pay the copy protection developers a royalty per CD protected. This is also supported by the fact that most protected games just have one protected CD, the play disc, like #4 of Enter the Matrix; more protected discs -> more costs for game makers. Other forms of payment would probably be undesirable to the copy protection developers, such as fixed time pricing (i.e. protect all your pressed CD’s for 2 years) because it transfers some risk of forecasting sales to them (i.e. they will be kicking themselves if they expected 500k sales and instead it was 2m, and charged for 500k sales).

As most programs I see around seem to be in CD format instead of DVD format - even the large ones which use a few CDs - does anyone know if the copy protection developers would charge more for DVD vs. CD protection?

I ask because it seems strange that since copy protection developers charge on a per disc basis, it makes sense for software companies to squeeze as much as they can onto 1 disc - a piece of cake if they use a DVD instead. But we don’t see many copy protected DVDs out there.

Or is there another reason, like technical, e.g. most copy protection schemes are not transferable to DVD discs.