is gut rehabbing a good estimate?

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so i was reading this http://www.biggerpockets.com/forums/67/topics/21771-gut-rehab-costs and got the definition of a gut rehab

"A major restoration project on an old house or other building, ripping out plaster walls back to the studs and rafters and replacing them along with some or all of the trim,"

on that link it said something like a gut job is about $40 a square ft.

so if i am really bad with estimating repair costs, could i just do a 1400 sq ft house and multiply it by $40? 1400*40= 56k. so that 56k would be the the estimate of the most i would be spending on repair costs?

200k (ARV) * 70%(my profit) = 140k

140k-56k (max repair cost) =84k

now obviously 56k seems like wayyyyy toooo much unless the property has completely gone to crap... but is that the most it could be?