I use a service that sends me a bunch of fairly trivial Google Analytics data. It costs $10/month for the equivalent of fifty lines of Python.
I know I could spend maybe two hours writing a replacement for it and set it on an EC2 host and probably never worry about it again, but those two hours are still non-trivial amounts of time: two hours of my time pays for more than three years of that $10/month. Plus, the API may be brittle, there may be edge cases I haven't thought about, and I don't want to add yet another thing to monitor and worry about.
Sometimes, yeah, you can automate things and roll your own dependencies -- and sometimes the calculus works out and it's a no-brainer. But I've found that homebrewing a $XX/mo dependency is rarely the best use of my engineering time.
Would you mind sharing which service that is?
briefmetrics.com
S3Stat (who another commenter mentioned) is also a great example.
It really depends on what your turnover is, where you make the most money, and what your time is worth (objectively, rather than ideally).
On the other hand it probably contains everything I could think of and it's still only ~$1000 a month, which is not a lot if you work as freelancer and run your SaaS on the side.