Quotation from "Small Stakes Hold'em"

I just read "Small Stakes Hold'em" for the second time and I wonder about what is said in the beginning under "Why This Book..." Sklansky suggests "Making well over $50.000 per year playing $3-6 hold'em is now no big deal." This could be done "because you can play two or three games at once". Is this expactation realistic? It seems a little high to me. Is there any 2+2er who could confirm it's possible based on experience? Anyone else with ideas and thoughts about it please post your views about expectations at low limit hold'em.