This is what I wrote six years ago. Even before recent sales I would have increased these prices by 30-50%.
1st series: non-existent
2nd, 3rd, 4th: all very hard to find, generally command $2000-3000 unless in terrible shape
5th: tougher than 6th and up, but not as tough as earliest series, around $1250-1500
6th, 7th: more common, around $600-750, possible less for the 7th gumless which is common
8th: tougher to find than you would think for some reason, I never had one, still probably under $1000
9th and 10th: pretty common, there was a seller at the Philly show years ago who had several of each, I paid only
$250 apiece for one of each, should sell for around $500 in my opinion
11th: non-existent
12th: lots of packs around, not as many full boxes, around $1000-$1200
13th: tougher, never owned one, probably similar to 12th in price
14th: one of the most common, $400-ish
15th: not terribly rare, but the 15th set has value, so still around $1000-1200
16th: obviously very volatile due to set volatility, couldn't venture a guess