Asterix Australia and NZ tend to use decimal odds which shows total payout. $10.00 odds means you get $10 payout for every $1 bet (ie, for the $10 bet at $10.00 you get $100 payout, which is $90 profit.) Payout = stake x odds. Profit = payout - stake.
UK uses fraction odds which others here will be able to explain better but as far as I understand it shows the profit relative to the stake. So $10.00 in decimal odds is equivalent to 9/1 (ie, profit = stake x fraction, so the $10 bet would be $10 x 9/1 = $90 profit). 10 to 1 would actually be equivalent to $11.00 in decimal odds if I've understood right.
As usual, USA uses some other system which I've not attempted to figure out.
NZ bookie has PSG at $1.65 and Arsenal $2.25 currently.