Ooh, vintage Rive Gauche parfum must be really wonderful. Envious... (I do have Calandre parfum, though - the usual Calandre Rive Gauche battle).
I agree that finding vintage parfums is quite a treat, and when I can, I jump for it. But it's so expensive! Some of the BNers here seem to bump into vintage parfums in local antique markets all the times, but I have not been so lucky (with a couple of sensational exceptions, though)
On ebay, the Guerlains are simply out of budget, the Chanels often too. Ditto for the Diors, when found. I only managed to get a Mitsouko 7.5ml for less than $100 simply because it was in Japan, and I guess the usual collectors were wary.
Joy is usually expensive, but sometimes one can find a smaller thing, like the 7.5ml black bottle, for reasonable prices. One has to keep checking from time to time, and wait for the lucky time when other people are not around. I actually also have Arpege, which I like a lot but somehow it doesn't make me dream. Perhaps it's just that the style is not as unusual in modern times (unlike, say, Joy or Diorissimo). Also, I cut my finger when clumsily trying to open the bottle.
I should also put a good word here for Tabu. This one seems to pop up now and then and is cheap. But equally sensational.