Pretty simple to understand since most of these places make money selling flavoring, bottles (huge profit to be made here), mods, tanks, coils or whatever. Most people who buy nic will grab some flavoring too. If you lose a nic sale to a competitor then you likely lose flavor and other related purchase as well. Better to make less profit then none at all especially if you can afford to do so. Places like Walmart do this all the time in fact they will often sell big electronics at or near cost in order to sell you other things at a profit.
I went to a local store yesterday as I am in the market for a Tesla M7 mod which they sell but was out of stock. Many of the mods they carry come from FT which they wont admit but I know they do. They sell $20 mods for $60+ and I almost caved since I understand shops have overhead. But I have another guy who gets me ANY clone for $40 or less who does not specifically carry the Tesla. The guy who sells his mods for less has sold me over $500 worth of hardware alone. I also bought lots of hardware and coils for friends and refer others to him so he makes money for sure.
I usually go to the more expensive shop to window shop and then have the other guy order what I want. Now if it was anything but the junk from FT (wont even debate the quality) I would consider paying higher prices. However I want a APO or Magma and the more expensive store only carries the cheap EGO-L, Ego-T and TOBH RDA clones. My other guy carries every popular dripper under the sun and not the FT versions for about the same or less then Ebay prices. I will end up getting a whole kit for under $70 even if I have to buy on Ebay and the store with higher prices makes nothing.
It's a dog eat dog world and I have stores all around me losing money since I got into DIY. Considering most places here charge $6-8/10ml and I was
vaping 4-6ml per day. It was costing me almost as much as buying cigarettes with hardware and coils factored in. If those stores would have been less greedy and sold 50ml bottles for $20 I would probably still be buying crappy
juice. They would of course make less profit but overall they would have made money where as now they make nothing.