For example, King size of the mattress on above link is for $215 (+ free shipping) after the discount, and Queen size is for $200. The BedStory website is showing 3-14 days shipping time - I assume they must be sending via international courier.
There's a black fabric version of this mattress as well, which seems to have exactly the same specs, but the price is a bit dearer for King size which I compared with that of the white fabric version.
Interestingly, Amazon AU has this particular mattress - a slightly thicker version listed on a special price ($5 cheaper with shipping) at the moment as well but it is showing a much longer shipping time so it may make sense to order from BedStory website if you want it sooner, assuming that timelines shown on both are accurate. I personally don't mind 25.4cm (10 inch) vs 31cm thickness; in fact I reckon 25.4cm may be a bit lighter and firmer which is better for me.
There are limited reviews on Amazon AU but the US listing has many more reviews if you would like to check.
I reckon one can't go much wrong with this price and the reviews available on internet. Pretty good deal even compared to totally unbranded mattresses in the market.
Exceptional value for these, no idea how they ship them free at this price