^I guess if people are collecting from the same couple of themes during the same years, it might not be too uncommon to see listings like this.
Update: The parts I had for Olivia's House and the small lamb set will just be going into my extra parts bins as there are too many parts missing, but the other sets are either complete or only missing a handful of things so I added those missing parts to Bricklink in case I ever find them at a store when I am purchasing other items. After going through these sets, I also determined that I had #21117 in there, as well as three of the figures from #10218. After I finish clearing this out, I will move onto another of my bulk buys that I had the time to purchase but not the time to go through.
As mentioned earlier, I'd like to pick the brain of someone working on the 3-in-1 line and find out how the process begins for designing those sets. I don't really collect those as much as other themes, but the ones I have (like Blue Power Jet) are just fantastic.
From a 20-year-old coworker in his Dark Ages: #7623 Temple escape, missing the plane and the ball; #7657 AT-ST; #7659 Imperial Landing Craft; #7661 Jedi Starfighter with Hyperdrive Booster Ring- ring only, missing the fighter; #7671 AT-AP Walker. All the minifigures are missing, but the rest of the parts look complete, or nearly so. Also the Sterilite tub with lid they were stored in... all for $20!
Did you warn him that in about 7-10 years he would probably want these back?