Well, I do it that cheap because I can. I'm not a mechanic for a living, and I'm not paying my bills by doing installs. I just like working on Subarus. I borrow a lift from a friend, so I don't have to pay for that. I already own all the tools I need, so I don't have to buy them. And, I take the wideband out of my car, so I don't have to rent one of those.
But, you are talking about a 6-7 hour job at least. If everything goes right, theoretically you can do it in 3 hours or so, but I have never had a single install that doesn't have a stuck bolt or something like that that needs extra attention. The most time consuming part is taking off the green brackets to pull the injectors. And, a FMIC requires grinding of the lower frame piece, and cutting of the bumper cover. So that takes a while as well.