I know very few people walking around a gun show, or anywhere else that matter with $1500 in cash. Even if I decide to take cash it's usually only $4-500, and I have to go to the bank the day before to get that. And most of my friends, who all make as much money as me, very rarely carry cash. I paid more in federal income tax last year than the average annual household income in the US, and my time is worth more to me than any "thing" I can think of. Whether it's an individual or a company, if you make it difficult for me to give you money then I won't. If you don't feel that you can take my check or debit card then you won't get much from me at all, because most of the time I am walking around with less than $50 in my wallet. I am certainly not going to waste hours of my time just to meet someone after a gunshow with cash, ok, maybe if they were coming to my office I would. And on weekends it's a rare thing for me not to be wearing cargo shorts and a tee short, because the untucked tee shirt conceals really well.
Last week I ordered a new pair of prescription shooting glasses from a local place. Went out of my way to buy locally, went down to get fitted, paid them their $500 (outrageous but they are a locally owned store). They called three days later and said sorry but the frames won't accept lenses with your presciption can you come down and pick out new frames. No I can't, I had them refund to my debit card and ordered a set from another shop, simply because they cost me time.
That's just how some of us view the world.