Not sure I understand. I'm assuming that by "small mom and pop cost", you mean THEIR cost, as in, what the LDS pays their supplier for an item. Of course the online store is going to have a lower customer price for the item than the LDS.
If an online store sells a product for LESS than the LDS is paying their supplier, then why wouldn't the LDS buy it from the online store?
For example. DGX sells an AL80 for $169. Ground shipping is $26. So total cost is $195.
If LDS cost (that is, what they pay for the tank) is $210 from Luxfer, and they sell it for $240, why wouldn't they just buy it from DGX?