Server costs much less then time and resources that you will spent on python.
As for speed, python is not such slow, and under slow i mean clear language speed, but as we use it coupled with services, streams, etc difference in speed is in some small epsilon. So switch not reasonable.
Talking about language speed only acceptable for soft with only in-language processing like Render, Encoding/Decoding, Math processing, etc.
As for concurrence and other things, it’s just a matter of hands, i had systems written in PHP that handles few thousand RPS without any problems.
Go is good for small scripts but not as main language for product, cause it has small community, not so many libraries. Which means that you will have plenty of bugs and situation where you need write libraries from scratch.