I think the problem with vintage prices is that they seem to change daily. One moment something's really hot and a few people are after it and the next day the interest has disappeared so the price can go for less. I was looking at some resealed Palitoy prices today from recent sales on eBay and thought they were the same or less than years ago. It is also the time of year as things don't seem to go for as much generally through the summer months, I guess due to people thinking about holidays or even the amount of conventions that happen (here in the States especially).
It's always hard to know for sure but I've always thought t's best to buy what you like at the price you can live with and you'll have to be prepared to take a loss if you should move it on. Of course it can work the other way like the AFA 85 VCJ's I sold on years ago to then re buy more soon after at a more inflated price. It was a hard thing to live with at the time but now it's a few years on the price from what I paid has risen by four times.....I bet when I sell them it will plummet to below the price I paid though