Okay, it look like i'm gonna have to explain it step by step.
When you buy a game, you buy the product itself, not the actual software. If i say i buy Super Mario 3 on the NES, that doesn't mean you own the copyright of the Mario franchise or the copyright of Super Mario 3 itself. No, you actually own the cartridge in which CONTAIN the data of Super Mario 3. Because you've paid for the cartridge, the cartridge itself is your's since you paid for the product, but you can't use the data of the game itself to make money out of it. You can then give the cartridge to your friend, or even eat it if you want, since you own the cartridge itself. You can dismantled the cartridge and put it back together as you will.
The hacker in the other hand play and use the software itself. He can't sell or make money out of it because the software is something own by a company. Hacking is not something illegal as long as they don't make money out of it. What about PC mod? They aren't different from hack game aren't they? Mod game aren't consider illegal as long as they don't make money out of it too.
A reproduction game cartridge make money out of the handcraft and the re-sell of the actual material with which the cartridge is based off. Since game can be legally re-selled, then it's not an issue.
A rom hacked for exemple are burn in a chipset. The person who will buy a reproduction cartridge will pay for the product itself, including the chipset in the cartridge, not the actual software itself who was burned in it.
Producing some cartridge without re-using some used game cartridge don't seem to be such an illegal issue either. New homebrew game are being released for the NES, Atari 2600 among many other. Recently, i buy a new title for the Dreamcast: Sturmwind. This disc isn't liscence by Sega, yet, should they get send to court to infringement of copyright?
The reproduction cartidge get his money from the the hardware itself, NOT THE SOFTWARE.
The software is why the cartridge exists. You're not buying an empty cartridge and putting a game of your choice on it. You're buying the game you want, which happens to be in a cartridge. Suppose you go to the store and you buy a shiny new Xbox 360 game for $60. Do you really think the $60 is for the box, manual, and disc(s)? Of course not. Most of it is for the game. How is a cartridge any different?
The pourcentage of how much money will get to who is already set by the publiser, whose is job is to sell a game. When it's about a used-game, the money isn't attribute to either the publiser or the developeur, since they already got their money on that copy. At that point, it's not about giving money for the software contain in the game, but rather for the actual material only.