Beyond the fact that there's absolutely no reason for you to post this, I'm not sure what you're looking at. I'm not a pro but I've been building sheds and things for decades and based on the pictures here I don't see low quality. Maybe I'd put more joists in the roof but Portland doesn't get a ton of snow so I'm sure it's fine. $2k is a fine price for that slab, especially compared to the pain of lifting 80lb bags of concrete yourself all day. People shouldn't be afraid of spending the money on a pro if they've got the money to spend.

Maybe he could have saved a few thousand with different subs (maybe) but your comments are nonsensical. I see tons of janky builds people post on Reddit and this is not one of them. You should spend your commenting time over there.