1x2 Arbitrage question

[BetExplorer]

Hi I am interested in doing sports arbitrage and had a look at the calculation behind 1x2 arbitrage. What struck me is that even though you are supposed to make a guaranteed profit it seems that in some cases you make a loss due to the two losing bets.

for example:

1 1.8 871.52
X 13 120.67
3 201 7.8


Total Stake 1000

Now all arb calculators (this is form arbcruncher) say 540 guaranteed profit but if you deduct the losing positions you get a loss?! Just do the maths for the draw X you end up with 689.39 i.e. a substantial loss on your total stake? I almost feel like I'm missing something I'd be grateful if somebody could point out where I went wrong.

And by the way this example is a huge arb it will be a lot worse for normal arbs where the margins are a lot lower...

[jetbet]

you have to check if the bookies accept the stakes you are thinking of.

sometimes yes and sometimes no and suddenly you are "******".

and even if you can place these bets, they may cancell them afterwars.

High arbs are not found often i think....