Assuming you are using annual numbers there, you are saying you have 55 users on Github. The relevant number isn't your IT budget, it's the salaries of the people using GitHub. If it's $75k per person thats over $4.125 million a year.
Does 0.15% of your budget matter? Does GitHub not make your team 0.15% more productive? Would the switching cost to a new tool be less than 0.15% of your total cost?
If you are doing that math and coming up with the answer that switching makes sense, by all means do it, but I would argue that your problems are bigger than your GitHub bill. I personally can't fathom working for a company that strapped for cash, I'd be looking for a new job myself.
