When it comes to cosmetic restoration, it's the same amount of work for a game that is common as it is for a game that is rare. Stripping the cp, putting on side art or stenciling , doing bondo work, restoring most of the electronics. Hours are hours. And that goes back to the answer of why there really isn't anyone doing extensive restorations "commercially". People don't want to pay what it's worth.
I hear what you're saying.
"What it's worth" is always subjective.
Many people wouldn't pay more than $500-800 for a Ms. Pac-Man or Pac-Man in decent shape. Nothing special - everything works as it should, no real damage, but you can tell it's been around for a while.
However, there are people who would easily pay $1500-$1800 for a fully restored Pac-Man (for example) if it looked like you were the first to ever play it.
So, "what it's worth" is subjective. Having a restoration business, preparing games in the hopes someone will buy them just wouldn't work.
However, as I mentioned before, "on commission" means that someone is inquiring about a specific game, to be restored and purchased upon completion. Obviously, the price would be agreed upon ahead of time. In this scenario, there is no risk to the restorer. The buyer would have to front at least half the cash, and the rest payable upon completion, etc.
This is the kind of thing I'm talking about. If you think that every restore to that condition commands $3000 regardless of the game, then you wouldn't get a lot of people inquiring about getting restores done. But if you were realistic about the pricing, because you enjoyed doing it, and weren't looking to get rich, then it could work out for both you and the buyer/collector.
This is just my opinion.