1. You don't believe top developers are intrinsically 'worth' the amount that FB/Goog/Amzn/ and many other SV companies pay, that it's not a net win for the company to have top talent.
2. You think that you don't need top developers, that really you're just going to be fine recruiting a bunch of B players, and it's some other 'thing' (business? Sales? Marketing? an 'idea'?) that will make you better than competition.
3. You are incapable of harnessing top development talent to produce adequate ROI that would justify top salaries.
Money is not my primary motivator, I love my job. I wouldn't leave just for more money. However, salaries in a certain ballpark are a strong signaler to how much a company values software engineers.
I think it's insulting to see developers significantly underpaid and have you attempt to justify it the way you do. If money is not your primary motivator, wouldn't you be OK taking a bit less salary and having that distributed out to other team members?