~50$ a month buys you a dedicated server with a Quadcore Skylake (i7-6700).
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.
Just want to point out that there's also the fact that if they want good unit economics, only a fraction of the $50 you pay the is going to paying for the hardware.
