DD went to this same event... and they all got badges (free). Why would there be interest in buying one retrospectively? Ditto for other badges same seller is selling! Some look retro, but most are quite recent.
It's also common to have extra badges to swap when you go to camps, my camp blanket has loads that I have swapped or received as gifts. I went to seaside sparkle with my rainbows and brownies including dd1 and dd2 it was fab
Many Guiders have got separate camp blankets for their Centenary badge collection. Badges from events that I was at are on my main blanket, but the bought & swapped Centenary collection is going on a big pink throw.