And it's quite possible that if everyone just bought in reasonable amounts then there would actually be plenty to go around.
It would seem that way. But it's not so.
Nature's model: a few people become essentially
distributors by buying it all and re-selling or trading it, getting it into circular. Less efficient in money.
Your model: everyone buys a reasonable amount, which means everyone has to contact their local B&M etc. Less efficient in time, has a higher requirement (group conformity and norming) with high negative effects.
Nature works in the ecosystem model for a reason. Penzance is distributed well by the current system; what's screwing it up is the appearance of clueless people who will pay way too much, raising prices across the board, and for more than Penzance. If you signal to manufacturers that you as a group are wealthy, they will raise prices. Sorry -- I mean impose price minimums.
I saw this same problem in record collecting. The market was efficient until outsiders entered who did not mind spending $200-$1000 for a rare vinyl or disc. At that point, everything went up in price and quality of new releases declined as all the sheep in the market chased the trend.
This is one reason why I do not support freedom, liberty, etc. The idiots always outnumber the good unless you impose standards that keep the idiots at bay. That is what people are trying to do here: set a price standard for resale of Penzance.