For years now I have both bought and sold advertising space and time. I can tell you the value of a digital impression in almost any setting, or what return on investment you might get from a 15 second pre-roll on a contextual site.
Space and time has value. And therefore so does my arse, my back and my belly!
Sure I will consider wearing your Abercrombie shirt or your Bench sweat pants, buts this biological billboard will cost you. A lot.
(Abercrombie might have to pay me more, have you smelt their stores!!)
There were some experimental companies set up to monetize the space that our bodies have, paying students to wear shirts with ads on them, but none of these companies seem to have made it work. Yet those same students will happily do this for free for all manner of brands. Oh, and they are paying the advertiser!
Personally I am turned off anything clothing with a big brand written on it... unless someone reading this cares to sponsor me...