I didn't say you couldn't live off of it, I replied to the person saying he's made enough money to shrug off losing 30-40 extra million had he signed that Dallas deal.
And even as far as being able to live off of it; pro athletes aren't living in a duplex, driving a Hyundai Sonata, and taking one vacation a year at a 4 star resort in Punta Cana.
These guys live in mansions (high property tax), drive luxury cars (expensive to repair, service, and fuel), travel to luxury resorts, wear luxury clothing. It's not easy to step back from that lifestyle and what's left over after you retire on 40ish million in career earnings (half of that goes to taxes) isn't that easy to stretch from age 35 until you die when you want to keep living that way.
I'd guess 40 mil in career earnings leaves you with like 8-12 million in the bank when you retire. Shit load of money but when you're 35 and you and your family have to live off it forever you're certainly wishing you had doubled that. (Anecdotally, Biz once said in an interview that Ryan Whitney retired with "11 sheets in the bank" off 35 mil in career earnings so I think my 8-12 range is pretty fair).