That would probably be 280 minutes of "build time" to do your build in 70 minutes. My math is: they are going to call your 8 core CPU 16 vCPUs, because it's something cloud providers can charge money for but Hyperthreading/SMT doesn't really speed up builds that much. It does do something, but 2 threads scheduled on the same core is not going to be 2x faster than one thread being scheduled on that core. (It sure will use 2x the RAM, though, while it sits there waiting to execute instructions. They will charge you for that too!) Then, because they are running on a 64 or 128 core CPU with the same TDP as your consumer chip, things are going to be really clocked down -- your desktop may boost to 5GHz during the build (assuming you got a good cooler and overrode the time limits for boosting; who doesn't, though?), this thing will be running at 2.5GHz. So you will need twice as many actual CPU cores to get the same performance.
I am being very pessimistic with these numbers, but I am continually amazed at how slow computers in the cloud are compared to my desktop. And when you're being charged by the minute, there is no incentive to make the computers faster, of course -- the business incentive is to make them slower! Buyer beware. (To be fair, they are getting a lot better Wh/build out of their system than you are. If you were paying for the electricity and cooling and got paid no matter how slow the build was, you'd make the same decision.)
I am being very pessimistic with these numbers, but I am continually amazed at how slow computers in the cloud are compared to my desktop. And when you're being charged by the minute, there is no incentive to make the computers faster, of course -- the business incentive is to make them slower! Buyer beware. (To be fair, they are getting a lot better Wh/build out of their system than you are. If you were paying for the electricity and cooling and got paid no matter how slow the build was, you'd make the same decision.)