That's a great "gotcha" question factory equipped with its fair share of snark via the clever use of the word "surely". Nice going!
However, it's not that simple. And, furthernore, you already know it's not that simple.
If we were talking about the one and only club in a town, we could boil it down to simple "facts". How much does the venue spend on entertainment vs. how much they profit. How many bands are available and at what costs? Any dipstick can do that math.
But we're not. We're talking about a MARKET...... a REGION.....MULTIPLE club owners that all come with their own variables such as booking agents, managers who have been given budgets, relationships with band members, etc.
We're also talking about musicians who place little or no value on their product. They don't see music as a business. They don't look at market fluctuations or see past the ends of their collective noses. Music is an outlet to them. The VALUE is about THEM. What am I getting out of this? Well, I get to dust off my toys and show them off to a crowd. I get to be up on stage and the center of attention for once! Money? Who cares about money? This is about ME! I want to play. I want to rock out for my co-workers. I want to get loud under bright lights. Put on a show? Dress the part? Forget it. That takes effort. This is about ME, remember? Negotiate higher pay? Turn down gigs if the pay is offensively low? No way! How to I get loud under bright lights if I turn down the gig? This is about me, remember?
No, it's not as simple from either end as "We can make you more money because we're better". If it were that simple, there wouldn't BE any hack bands.