i find when trading XJO options it helps me visualise it by thinking of the premium in terms of points rather than $. Commsec is probably trying to shoehorn XJO into their existing systems by applying the 100 contract size and the $10 per point multiplier to come up with the prices they're showing, which i don't find all that helpful, but YMMV.
you multiply Commsec's prices by 100 to get the premium in terms of points eg. for your long 6700 straddle you're paying say 96 points for the calls and 125 points for the puts (i usually assume 1 or 2 ticks their side of the mid, since from experience, you can usually get that on the XJO or the major large caps, you don't have to cross the full spread). that's 221 points total, so your breakevens are 6479 and 6921, you need a blowup of that magnitude or larger within the option expiry to profit, a 1% move certainly won't do it.