At least for the 1969 model year, a coupe to RS conversion is NOT simply adding hideaway headlights and a couple of badges. Yes, it is a trim package, a very elegant and complicated trim package. The differences are many - the RS variations from the "standard body" include:
different outer fenders, different inner fenders, different grille, hideaway headlights (based on vacuum actuated, articulating, headlight mounting bracket to rotate the headlight covers in and back in the open position), inner and outer headlight door covers, vacuum cannisters, mounting brackets for the vacuum cannisters, vacuum reservoir, relay valve and the associated vacuum lines, different headlight switch with vacuum hose connections, different windshield wiper switch (2 dentent positions, first detent routes water to the windshield washer nozzles, second detent routes water to the headlight washer nozzles which spray water on the headlights), headlight washer nozzles, diverter valve on the windshield washer pump, water tubing from the diverter valve to the headlight washers, and even a difference in the front header panel to accomodate the headlight washers themselves --- even down to the miniscule items like the bracket that holds the windshield washer bottle - it is different on a RS vs. a base coupe or a base coupe Z28. And this doesn't include the Style Trim RPO items that are a part of RPO Z22, the RS package.
It is very true that a base V8 RS Camaro is not valued as highly as a Z28 or other high performance variants. However, you would probably be very surprised as to what a very nice 69 RS will sell for. Just try to find one listed in Hemmings, not a RS/SS or a Z28 w/ RS. Try and find a nice, fully functional 69 RS, they are very few and far between.
In a lot of ways, if done accurately and correctly, a more difficult conversion than a base coupe to Z28. Now a Z28 with the RS package - that is a very cool ride.