Per ticket. You can buy unlimited amount, but only 1k per ticket. I tried chocobo betting myself and saw a loss over time. I would win if I was very lucky, but profits were minimal. I would sit there at the board and figure out the birds' chance of winning. It took me a while, but I figured out how to use the tote. Just anyone who is confused, I'll explain.
http://images2.wikia.nocookie.net/ff...2007%29-10.jpg
Let's say you bet 1 and 5 to win, based on the chart above, your bet would come out to 3975 gil per quil. Since other "players" are bidding, your bet would go down or up, based on how many NPCs bid on it. As you can see, 1-2 is the crowd favorite and will most likely be the winner. This is not always true, but in my opinion your best bet to see anything out of the race. One thing I found true though, it's almost never SS/SS/F/F who win, it's usualy A/B/A/S birds. These birds almost never get effected by enemy attacks, so I believe that RSC and DES to be a big factor in deciding the winner of a race.
Just my 2 cents.