Money comes from anywhere, tech talent is fixed in supply.
Startups offering more cash has no implication that they must generate revenue (although that's obvious to building a good business). The point is that operational costs exist - and so a business must already have cash to exist - and increasing costs for better salaries and benefits is a better trade-off than increasing equity which is mostly worthless anyway.
Also global tech talent has more supply than demand once you get past the SV/HN bubble. No serious startup has failed because they didn't get the perfect engineer.
Engineering talent is in oversupply across the US and definitely across the globe. You can easily hire PhD level talent from Brazil or India. Also FAANG companies have long ago exhausted the best talent available. Most of their hires at this scale are no better than engineers elsewhere, it's more about the interview process, benefits, location and internal politics than raw quality now.