That's $6/minute, $360/hour. Granted, if you're using it at a scale approaching FTE costs, you probably want at least some reserved capacity and you're likely not paying face value, but then the comparison was never going to be rigorous anyway.
That's not even the main problem with the comparison. Suppose it was actually $6/hour. Even that's >$50k/year, indefinitely.
How long does it take your team once to make that resource consumption go away permanently? An hour? Even a month? You'd still be ahead.
Working for a smaller digital agency, while using .NET Framework, and then moving to .NET Core (now just .NET) this savings was felt. Using a performance profiler and slightly complicating the code a bit (at least in terms of the documentation for the CMS we use), I was able to get the code in less than the minimum recommended requirements for the base CMS software, without having to alter the source of the CMS. I did this with the Umbraco CMS, but also started using it in 2013 when the documentation was lacking, so reading the source code was a requirement to getting as much as possible out of the software.