Sure, there's a couple on there right now (at high prices though, especially when you factor in shipping)
Recent completed sales for an ADM-3A on ebay:
192827478293 $220.00 + $70
323743149867 $158.50 + $73
254170169347 $45.00 + $125
332825368751 $299.95 + $90
The guy who got one for $45 (+$125 shipping) got the best deal.
You may consider these prices "high", but these terminals are sought after by many vintage collectors because they were commonly used in the late 70s/early 80s.
I monitor terminal sales on ebay often and although I haven't been gathering records, the prices above are about average for what you should expect to pay for highly sought after serial terminals at this point (e.g. ADM-3A, VT100). If you are patient, you can find better prices (the $45.00 unit only had 1 bidder).
Remember that just because these things were once ubiquitous and people weren't interested and therefore were cheap to buy, that isn't the case anymore.
Sure, you used to trip over VT100s lined up on the curb outside some University surplus warehouse in the 90s, but those days are 20-30 years gone now.
Most terminals were scrapped long ago. What's left is what's left.