Earlier quoted context omitted.
> Building and running your own software team is probably around $5M/year Do people just pull random numbers out of their ass with no actual experience? 99% of developers do not live in Silicon Valley on 1m salaries.
Cost is not just salary. To begin with, health insurance and other benefits. And they'll need dev environments, they may need additional cloud resources depending on how the project goes, and there will be additional overhead when the team interacts with other departments.
And to be honest, I'm not convinced a moderately complex in-house crud app would really require 5 senior developers but impossible to have a strong opinion on that based on the details that OP provided. It might be a one man job, it might take a team of 10..