>>10000758I basically refuse to sell sets on bricklink if they are not 100% complete other than a few caveats.
Sometimes stuff like rubber bands or string are very hard / prohibitively expensive to replace. Relatively exclusive old vintage parts can also be a huge burden, but even then I still try to replace them so I can sell the set as complete, which you can charge a premium then.
This lil bastard in yellow is $20 because it was only in two blacktron sets. Another classic example is the blue palm tree top which was from a huge pirate ship (also $20).
If you're going to sell a set incomplete, it had better be for a pretty decent discount or good reason - more than what the missing parts are worth. Make it feel like a good deal at least. Maybe list it on ebay instead.