I really doubt that "sweetening the pot" is banned considering that WB put in a substantial pot for MK9 in 2012. Unless policies changed since then. 
I found this on some random 
E sports site... don't know how legit this actually is: 
Evolution 2013
Jul 12th, 2013 to Jul 14th, 2013
Evo 2013 (SSFIV:AE)	-	                        $16,370.00	
Evo 2013 (Ultimate Marvel vs Capcom 3)-	$13,020.00
Evo 2013 (Super Smash Bros. Melee)	-	$6,960.00
Evo 2013 (Injustice: Gods Among Us)	-	$5,820.00	
Evo 2013 (Street Fighter X Tekken)	-	$5,730.00	
Evo 2013 (King of Fighters XIII)	-	        $4,270.00	
Evo 2013 (Persona 4 Arena)	-	        $4,000.00
Evo 2013 (Tekken Tag Tournament 2)	-	$3,550.00	
Evo 2013 (Mortal Kombat 9)	-	        $2,330.00
	
		
	
	
EEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE Sports. 
We in there.