Yes the series 1 240's are more desirable for plenty of reasons and always will be. Yes they made more 280's, but if you ask me they rusted or got trashed just the same as a 240's so one could argue about which is harder to get. When I was looking to scratch my Z itch, I actually preferred a 280 over the 240 just for the refinements and dependability (I've owned a 240 long ago). Since I got mine 5 years ago, I've seen prices go up at least double on average for restorable 280's. Throw in "restored" cars and the prices have climbed higher. I see asking prices of 8-30K for 280's on a regular basis. I'll add that prices can swing pretty wide from west coast to east coast with the higher prices being in the east so also toss in the regional factor. I've ruminated on value for a while, and wether you've brought back a 240 or 280 from the brink, I think one would be lucky to break even cost wise but the enjoyment factor is priceless, any yes, I know it's a disease. My wife occasionally asks how much more to finish the Z and I always tell her it's a never ending story but it's worth a lot more than what I paid for it ?.