macbook pro's are faster than any VM you can pay $50 a month for.
The fastest Macbook available right now has about the same CPU power, and comes with less RAM. So no, the Macbook isn't faster than what you could get, but it makes sense if rented CI infrastructure isn't faster for that price.
First provider I checked has a multiple server offerings with quadcore i7-6700 and 64Gb DDR4 RAM for 39€/month [1].
1: https://www.hetzner.com/dedicated-rootserver/ex41s?country=g...