Funny the mention of a 71 Riviera. That was the other car on my list of "wish I had back". I bought one when I was 19 years old - gold with a black vinyl top and, of course, the 455 engine. It was a bench seat, column shift car but I didn't care, it was a Riv. About a year after purchasing it, a state cop hit the left front corner of the car and caused considerable damage. The car was repaired but never seemed right so I traded it in on, of all things, a 73 Mazda RX3. That's another story that involves hot dogs, Coca Colas and the dragstrip.
A few years ago an auction near me featured about twenty 71-73 Rivierias that a local eccentric collected. All were well worn and every one of them brought strong money. I did come home with a 3300 mile 1981 Eldorado that quickly became a money pit.
Mark - your assessment of the Riviera market is spot on, everyone thinks their car is worth a king's ransom.