It's more likely you'll encounter miniature jar of mayo enthusiasts on eBay than it is that a bunch of them will by chance be at your garage sale. This would a

It's more likely you'll encounter miniature jar of mayo enthusiasts on eBay than it is that a bunch of them will by chance be at your garage sale. This would account for at least part of the difference. The other part can be accounted for by saying Barack O'Bama autographed the jar. Also factor in shipping costs, which usually justify an increased price of around $10.