Buy it or build it: Etsy

You inflated numbers from your initial calculations, but I don't believe you inflated them enough. How do you expect a team of 20 to recreate an entire company in one year? Here's some things that I believe you missed:

- You need a team of product and project managers to put in time to plan the product and a high-level road map. The more granular product decisions are able to be performed in parallel to the build, if building the product in an agile fashion.

- Etsy has an amazing engineering culture that cannot be constructed if the developers are just focused on delivering the product. This culture has lead to many internal tools that help with site reliability.

- Etsy has already built a team of strong contributors. If Amazon were to build their own Etsy-like marketplace, there would be recruiting costs and false positives which will slow down delivery.

This list could go on and on, but is meant to illustrate that there's more to this sort of project than engineering, marketing, and infrastructure.

This is an interesting thought experiment.