Maybe it's just me but it blows my mind that this tiny thing cost $20k. I wish building stuff in the West wasn't so expensive.

True, things in the west tend to cost more than elsewhere (I'm in Seattle WA.)

My mother-in-law lives in rural Missouri and had her 6x10 bathroom remodeled in 2025. Full gut replacement of everything. Total cost: $5600. I got a quote for something similar in a bit larger bathroom in our house in Seattle. Quoted price: $31,000.

Labor is a good chunk of cost, and the OP presented that he simply didn't have the time available to him to do that work himself. On the other hand, I built 20-ish feet of fencing for our backyard this summer, matching an existing design we had done several years ago. Quoted price from the same company that did it the first time: $9800. I did the work myself. My total cost: $1400.

That works out great, right? I also have a significant investment in all the right tools: compound mitre saw, construction-grade table saw, nail guns, impact/hammer/regular drills, angle grinders, power sanders, every drill bit in captivity -- I don't really lack for anything. These make a huge difference in the workmanship of the final outcome.

And that was just a fence. I've considered building an external office here at our house. When I start to take into account the scope of converting an outdoor shed to an acceptable backyard office, I hit the brakes. Electrical power under proper permits, adequate security, something that holds up under our weather, potential water/sewer access, and sufficient space to work (I can't live without a whiteboard)...there is more scope than meets the eye.

All things considered, I think the OP did a pretty good job here in terms of cost control and recognizing what he could do (windows) vs. needed someone else to do (proper electrical.)

A lot of that cost is labour. Look at all the spots it says "contracted" in the breakdown. If you can do a lot of the work yourself, then you can save a lot of $$$, but it's a tradeoff of course. (They also could have saved quite a bit by just having a window unit AC, but that's up to them.)

Seems about right given labor. If you do most things yourself other than electrical, can probably cut cost a fair bit. But tradespeople are expensive when you can even get them.

It's probably more expensive now. No date stamp on the article but was first submitted to HN in 2023.

The building is cheap, the labor is expensive. I built a much larger shed in volumetric space last year for 1/4th the cost.