Just in case anyone is unaware: Lego does in fact ship single pieces for free, if you lose one.

Just tacking on to mention the smallest parts are most likely to be lost, they’re the ones that - if dropped - seem to bounce and roll under a refrigerator or into the ether. They don’t give extras on the larger parts because they’re not likely to be lost. Frequently enough all it takes is a violent/careless bag opening to send the small pieces flying.

Being aware of this, I am waiting for a solution to what to do with the leftovers besides chuck them into a landfill. The problem, of course, is scale. No one is mailing 3 screws and an Allen wrench anywhere. Maybe once you hit 5 pounds of spare Lego . . .

I've often thought about this when assembling Ikea furniture. I have never been shorted. There's got to be someone at Ikea with the job of calculating the target acceptable ratio of over/under supplying small hardware pieces. I figure they can probably give out thousands if not tens of thousands of extra little screws/dowels/plastic bits before it exceeds the cost of missing just one. Between the cost of a support call, maintaining a supply of spare parts, labor and shipping to send out replacements... not to mention the less tangible to calculate loss of reputation to the brand. Quite interesting to think about at scale.