It's the price for a not-very-specific vcpu. Your performance could be better on the A family, more than offsetting the price difference. Of you're really considering the choice - you should test your workload on both. Or maybe they save you time in a different way - for example you save time not having to run a virtualised linker after cross-compiling.

It's the first generation of the hardware. I'd imagine the costs will start to come down over time as they ramp up the supply chains.