I doubt an indy shop is going to use OEM parts though. They will buy them from a local parts store and will be considerably cheaper than Toyota OEM parts.
In a perfect world one might change the gasket only and everything will be fine no matter what. In the real world what will happen, as surely as the sun rises in the east, is that if the gasket only is replaced and the timing chain jumps, breaks, rattles due to a bad tensioner/worn guide or whatever 20k miles later that the majority of people would be posing a question on this forum about being ripped off by an incompetent mechanic who changed the gasket and surely was the cause of any current problems.
I've seen countless times where someone did not want to proceed with a proper repair and would even sign off on a copy of the repair order acknowledging they will not hold the shop responsible for the car owner's shortsightedness. When a problem does develop many will not remember signing off on it. Some even claim to have "lost their copy" and in a few cases when presented a file copy have even claimed their signatures were forged or they "don't remember signing that paper".
If the gasket repair was being done on a low miles engine, even as a warranty job, then I could see the gasket only. When you're well into the 6 digits mileage wise, especially if the oil change regimen has been lax, then it's best to be prudent if you're going to keep the car.
Of course, that brings up the point about ethics of the car owner who would be willing to slop it together with the intention of dumping it off on a dealer as a trade or on a buyer through a private sale.