The most practical way I can think of it is like this: your friend can buy a '93 with less than 200,000 miles for the same price or possibly much less. YES, your car is probably in better shape cosmetically and mechanically, but does that matter to said friend?

It sounds like you're asking "What is this car worth to me?" rather than, "What is this car worth to my friend?"

Question: As noted, half a million miles is a lot of wear for ANY engine or tranny, no matter how well maintained - will you be there to help this friend swap a tranny or rebuild the engine when something finally goes? If so, maybe it's worth your asking price.