Wow, most of this is such bullshit.
> 1. A concentration of team members in low-wage regions, since it is a better deal for them, while we want a geographically diverse team.
Wrong. You are assuming that people only care about maximizing disposable income. That is plainly incorrect. The vast majority of people won't move to a 3rd world country with a much worse standard of living, language barrier, uproot their family's life, have safety issues and what not, so that they would have potentially 2x - 5x spending power. The reality is cost of living around the world differs, but not to the extent that this influences a large number of people in an organization into switching countries.
> 2. Team members in high-wage regions having less discretionary income than ones in low-wage countries with the same role.
Wrong. And, also, WTF. It is also not your place to determine people's discretionary income, who do you think you are - their mum? a slave owner? A TV, a Macbook, a car, fuel costs about the same everywhere in the world, because there's a global market. That's true for pretty much everything but rent and food. And you're also completely unaware of various tax rules in countries that may give long-term benefits / short-term tax hikes that end up fundamentally changing earnings and lifestyle. Not that any of that would be your business, but if you're going to do that using this justification, you need to do extremely detailed and sophisticated research. Otherwise, your social equality goal will definitely backfire.
> 3. Team members in low-wage regions being in golden handcuffs and unlikely to leave even when they are unhappy.
Wrong again. Any employee can go work for another company that hires remote workers. Most of these companies don't adjust salaries to some perceived cost of living factor, so, in effect, you are making yourself incredibly uncompetitive with this practice. For instance, I am extremely good at what I do and I command the global market rates that reflect that. Therefore, I would never consider working with Gitlab.
> 4. If we start paying everyone the highest wage our compensation costs would increase greatly, we can hire fewer people, and we would get less results.
That's the only actual reason. If you paid competitive rates globally, you'd spend more money.
> 5. If we start paying everyone the lowest wage we would not be able to attract and retain people in high-wage regions.
LOL, let's pretend that's a thing you could do even if you wanted to. In fact, if you could pull it off, you'd do it.
To sum it up, you just lost a lot of people's respect on here by giving a bullshit answer to a serious question. You should've told the truth, people generally respond well to honesty. It is not unreasonable that a startup (or, indeed, any business) would want to reduce costs as much as possible. This BS response, that tries to make it seem like you're doing everyone a favor by not paying global market rates, is just a turn off for most intelligent people.