Hi Bob,
"Surely, in the WAS/SEA example, it doesn't mean you bet 700 to win 100!"
I'm not sure, but maybe it just means that. According to
this :
"... The difference between the two will continue to climb as the disparity between the favorite and the underdog increases. In a boxing match it would not be unusual to see odds such as:
Joe Louis -700
Ray Leonard +550
In this instance, those betting on Joe Louis are being asked to risk $700 to win $100, while Ray Leonard backers are risking $100 to win $550. ..."
I know that in your example it's not box but basketball, but... Who knows, maybe the difference between the teams is such big.