In the big grand prix events - like Berlin with the possibility of selling close to 100,000 seats at 120 ea plus TV rights, it’s perfectly reasonable but in locations that can’t fund their own athletes, it’s a question of priorities.
I flat out guarantee that Bolt’s appearance in Toronto will have ZERO effect on the sponsorship of any Canadian and interest in track will fade once he’s 2000 ft in the air on his way home.
BTW, Bolt’s contract also contains a clause specifying who else is allowed to enter the race. I heard no Tyson Gay but I’m not sure who else.