There were a few cases where I completed (or nearly completed) a set from a single bargain bin. The largest of these sets had 24 coins in it, the second largest was, I think, 16 out of 23 (I've since got two more of that type).
For the record, I'm talking about the situation where a particular bargain bin happened to have very many coins of a single nice-looking type, and I decided to pull out as many different dates as I could find. The 24 coin set took me two hours crouched over a single 10 ruble (~$0.15) bin (during which I also found some other cool coins not of that type), but I definitely loved every minute of it, so I don't complain

Not sure if it counts under the OP; I certainly did not set out to complete any set when I started with the respective bin, and in many cases (not for the 24 coin set, which I checked in the coin shop's copy of Krause, but certainly for most of the others) I had no idea how many coins the full set would have had!
In particular, in the 16/23 case, I suspected the set had 15 coins until I accidentally found the 16th, and then thought it had 18 - I didn't find out that there were 23 (there was one year where the mintage was much smaller, so I didn't get any examples of that year) until checking it on Numista later.
Also, a few years ago some guy I barely knew gave me a nearly full set of US
State Quarters (that I never otherwise collected). I don't think that counts, but whatever.