I've done some cost analyses between our AWS and DC infrastructure.
To come up with our on-prem compute costs, we baked in the cost of power, real estate, staff, taxes, network infrastructure, servers (both in-use and in reserve), etc. On the AWS side, we used 3 year RIs and Savings Plan. After all that, there was around a 30% cost advantage on-prem. That's non-trivial, but not as big as one might think.
Outbound networking, however, is ludicrously cheaper on-prem. It's about 85% cheaper on-prem than in AWS. Bandwidth is not expensive outside the public cloud.
In fact, egress volume is the #1 cost driver for us moving a service on-prem or building it there to begin with. Some of the AWS managed services are also very pricey, but nowhere near the egregious markup of egress bandwidth.
To come up with our on-prem compute costs, we baked in the cost of power, real estate, staff, taxes, network infrastructure, servers (both in-use and in reserve), etc. On the AWS side, we used 3 year RIs and Savings Plan. After all that, there was around a 30% cost advantage on-prem. That's non-trivial, but not as big as one might think.
Outbound networking, however, is ludicrously cheaper on-prem. It's about 85% cheaper on-prem than in AWS. Bandwidth is not expensive outside the public cloud.
In fact, egress volume is the #1 cost driver for us moving a service on-prem or building it there to begin with. Some of the AWS managed services are also very pricey, but nowhere near the egregious markup of egress bandwidth.