I've seen places which will rather hire 10 developers getting paid $80k a year than two developers getting paid $400k a year. You get what you pay for. The number of managers who will not hire someone getting paid more than them is astonishing.
1. Much less likely to challenge them.
2. Numbers look much better.
3. When things went south, there would be someone to blame.
4. They are not great at assessing and contextualizing skill and experience
Additionally, with good leadership 10 x $80k would almost certainly outperform 2 x $400k developers.
There are lots of complex failure modes in a system like this, and minimizing them is an advanced skill. The learning curve for a competent generalist senior engineer to get good at these kinds of problems is significant. Designing and implementing a national securities exchange is a big deal.
This is a place where you want either experienced developers who have worked on other stock exchanges, or at least FAANG engineers who've worked on systems with analogous challenges. This is not a place you want to skimp on salary.
Of course OP thinks that $80k is a good salary for a developer so that ought to tell you how competent she is.