I bought mine pre built back in 2017-18ish maybe? It was about 3k then, so in todays market probably $7500.
I wanna say it’s like 14x10 or so. Fits a absolute shit ton of stuff comfortably and I wired it last year so it lights up at dusk like the shop and LED interior light plus a outlet for battery tender duty.
It has higher than average ceiling height so I can store the roof cargo box, lumber, ect up high and still have 7’ or so of headroom. Big shelf across the back and tire rack on the wall nearest the pinned door.
At the time I couldn’t build it for what I paid, especially since I’d need a second person to spend a entire day on the project with me (and definitely three trips to Lowes as with any DIY in a field outside of your trade).