Also, the "plus" part covers both overhead and profit. So, depending on what your overhead situation looks like, profit can still be minimal or non-positive.

Sure but the "plus" part is capped [1] for cost+plus.

If you're buying AWS compute through GSA I bet the rate is more than AWS's costs + 10/15%.

Or if you purchase say post-it notes from Staples; I bet they're going to be way more than the cost of paper+glue*1.15.

[1]: https://www.acquisition.gov/far/15.404-4#FAR_15_404_4__d941e...