If my math is right, that makes it $6.77 per month for a full time f1-micro instance. That's comparable to DigitalOcean's prices.

( 0.013 dollars/hour * 24 hours/day * 31 days/month ) * 0.70 discount = 6.77

Your math is correct, but you have to remember that Google compute instances don't include disk storage or network transfer - you have to pay for those separately, which drives the cost up higher.

It´s even cheaper if you run the vm non-stop. They are offering sustained use discounts.

dfbrown factored that into the calculation (by multiplying by 0.7)

Does the f1-micro use SSD drive?