I stopped collecting full boxes several years ago, so I don't really have my finger on the pulse of the current market, if in fact there is one. Most of the time, it seems like people put these on ebay at outlandish buy-it-nows and they never sell.
Here is my perception of prices in the middle part of the decade when I was active with them:
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
Again, likely that any of these would sell for less now due to general depression of the market. All of the above are for the most common color variation, 8th blue or 5th yellow would go for more.