Who even remotely suggested that people who choose not to pay in excess of 25% in fees and instead go elsewhere cost you a dime? Where do you come up with this pretzel logic?
If you still think this is about choosing not to use Reverb versus choosing to not consummate the deal you started via Reverb and steal their service, after pages and pages of this, I don't know what will get you to understand the basic argument here.
Tagging on to @Wilmingtonian 's point - I am by no means an expert in business analysis or economics, but consider this:
Most if not all businesses have certain fixed, or at least inflexible operating costs that impact their bottom lines. Those fixed operating costs are covered by consumers paying for them via the purchase of the goods and services offered by those businesses. The more people that pay for those services, the less expense per consumer for those fixed costs. This is the idea behind economies of scale, and one reason why something produced in large quantities is often more affordable - lower production costs. This is a gross oversimplification, but think of being a business owner who buys a machine that produces 100,000 units versus 1,000 - which one would spread the cost of the machine into the profits generated by the sale of the products more efficiently?
One of the reasons it is unethical to use Reverb to advertise, then circumvent them by taking the transaction elsewhere is because the fixed costs to those businesses are there regardless. They are pushed onto those who do pay them by those who don't. One is literally stealing the services that Reverb pays out of their business expenses for us to use. And because they or no other company magically makes money out of thin air, it has to come from somewhere, in the from of added cost to the consumers to choose to both use and pay for the service. This argument, by the way, does not work the other way around. Reverb is the one offering the service and is not committing theft by charging fees deemed too high by anyone. Sellers may be trying to make money, but they are still
consumers of Reverb's service and agree to the terms of sale upon listing an item.
There is a counterargument here, which is that the companies are held between two opposing forces: one, to offer the service at the lowest possible cost to remain competitive; and two, to offer the service at the highest cost and least expense that they can to maximize profit. Given that businesses are often first and foremost out to make money, it's understandable that they would lean toward the latter option when possible. Corporate greed is a real thing - I won't deny that. As consumers in a capitalist market, however, we have the ability to keep that tendency in check to some extent. We vote with our money, and we tell businesses that we don't like for whatever reason (too expensive, poor service, etc.) that we don't like them by choosing not to do business with them -
not by stealing from them. Two wrongs don't make a right.
Again, if Reverb's, PayPal's etc. fees are such that one considers them too expensive, they simply shouldn't use those services. Feel free to use whatever other service you would like. Talkbass is certainly much more affordable than Reverb, but I would bet that Reverb ads for bass gear are going to garner far more eyeballs than identical items listed on the TB classifieds, not to mention that the average TBer is probably more likely to be hip to the bass gear market and thus harder to bargain with. You get what you pay for - in this case, the size and scope of Reverb's brand identity.
I really am firmly of the opinion that advertising on Reverb, then taking the transaction elsewhere to avoid the fees is tantamount to theft. Reverb has every right to, and frankly should issue warnings and even ban those who do this repeatedly from using the service. I am sure Reverb is aware that people are doing this and probably has a strategy, i.e. the extent of tolerance or a system of how violations are dealt with, probably based on what will be most profitable to them in the long term. On that note, the trend toward these companies moving from individual sellers to corporate sellers such as music stores makes sense. If the little guys are going to rip them off on a micro level, it is more profitable to them to offer their services to businesses who have a lot more paperwork, red tape, i.e., accountability to perform above-board transactions, and thus ensure that the marketplace services will get their cut on a macro level.