Well I've worked out it isn't, just sorting the maths out now
Must be the reciprocal of an arb - I initially thought that the two lays were like 2 backs - but I think I have to compare the liabilities instead of the lay odds. If the two lays were less than 2 then it would be an arb I think.
Edit
Yep I've worked out the odds, it was a dumb question, but I've learnt from going through the maths
Two lays at under 2 would be a garunteed profit at betfair yes. In Horse racing there was a profitable system to lay all horses in the race at 1.4 at the off, over the course of the race often two or even three and very occasionally four of them would be taken.
Say you layed £10 at 1.4. If the race just has one horse in front with one furlong to go and he is pulling away only one of the lays would be taken and he would win and you would lose £4.
BUT if it is close and one looks like winning then another comes flying home, or one is a long way clear but falls at one of the last fences, or if a horse outright wins but is disqualified later, you would have two of them matched. That would be £6 profit, you have two bets for +£10 and -£4.
If three horses all look like winning over the race you would be +£26. I read at betfair it was optimum to lay at 1.4 but this was a few years ago. If you did lays at 1.1 then obviously you would only be losing £1 a race on losses, but it would be rarer that a horse goes down to 1.1 then loses than going to 1.4 and then loses.
If you get a chance watch some of the races go in play and you will get the idea. Volitility is your friend.
I am almost all the way through a 10 bet requirement at Blue Square and have won every bet to date! I have mostly matched these and have gained or lost a few pence per bet, so if I did underlay them all I would have been a few quid up now and even if I lost a couple at the exchange I'd probably still be a couple of quid up or break even at the worst. Hmm...
Anyway I have a question regarding underlaying. Do you use a certain criteria when underlaying i.e do you only underlay if the bet is the favourite or below certain odds?
RE Underlaying: No i personally just guess and put in an amount i am happy with. If its a £25 freebet i would probably lat £15 or something like that. I dont work out the returns but i know that an exact match at 11s+ is going to be a Net £100 or more profit if it comes in and if it doesnt then its £15.
If/When it comes in its a nice windfall then but when it doesnt its £15 banked and job done.
Underlaying at low odds doesn't make much diffrence to your profit, but underlaying at high odds does.
Consider a £10 bet at odds of 1.1 (back and lay the same and no comission )
If you bet £10 and lay £10 you get the same profit either way.
If you bet £10 and lay £9 you make a £1 profit if the bets wins and a £1 loss if the bet loses
Now consider a £10 bet at odds of 11.0
If you bet £10 and lay £10 you get the same profit either way.
If you bet £10 and lay £9 you make a £10 profit if the bet wins and a £1.00 loss if the bet loses
If you're betting on arbs then the loss if the bet loses will be 0 but the gains will be much higher. Underlay at high odds. Don't overlay unless the offer dictates that you should.