Your question (and some of the answers) seem to imply that players need to store large quantities of picks, presumably to keep up with the ones that get lost. I realize that I'm probably the odd man here, but I can't remember the last time I actually lost a pick....except when I loan one out that doesn't come back. I replace them when they wear down. Once every 4 or 5 years, I'll buy a dozen, and put a spare pick in each guitar case.
The trick to not losing picks is to think of them as a vital piece of your gear rather than disposable. When playing, the pick is either in my hand or between my teeth if I need to finger-pick a passage. When I put down my guitar, the pick goes between the strings at the top of the neck. It will be there when I pick the guitar back up. When I pack up my guitar, there is a ritual of coiling the cable, putting away the tuner, folding the strap, etc. I don't close the case until everything is accounted for...including the pick.
I understand how players lose picks. I can understand the need to have a spare handy if you drop one on stage, but the concept of buying hundreds and scattering them around just seems like giving in to chaos.
BTW, somebody just asked this exact same question on Quora...was that you?
Playing guitar since 1964