yes, I did pass high-school maths
My horrendous mathematical skills are saving me from insanity, and this is how:
In Beijing the currency is the renminbi, which is at approximately 2RMB to 1 Malaysian Ringgit. This, of course, means that I walked around in Beijing for six weeks blissfully dividing all the prices by 2, which is rather like carrying around a little portable 50%-off Sale.
In England the currency is the pound, which is at approximately £1 to 7 or 8 Malaysian Ringgit. This means that currency conversion takes place in my head in terms of £1:how-many-weeks-one-can-live-on-this-amount-in-Malaysia, which is rather like carrying around a ten ton ball and chain of guilt and general aghastness.
It works like this: I have no idea what the direct conversion rate is between the renminbi and the pound, and I suspect that it is a larger number than I care to know. And because my maths is That Bad, I have not figured out this direct conversion rate. Therefore, when comparing prices I always have to convert from pound to Malaysian ringgit, and then from Malaysian ringgit to RMB.
This cumbersome process of conversion takes an additional effort of calculation, which my mathematically-retarded brain isn't naturally disposed towards. If I were a better mathematician, the conversion would be almost instantaneous: I'd be walking through Topshop and instantly realize that for the standard £45 skirt I could buy precisely RMB658 worth of skirts (approx. 22 skirts), and also that RMB658 can feed someone for a month, and then some. Instead, I stand in front of the rack and squint at the number for a while, realize that it's too much of an effort to multiply 45 by 7.6 and then the result of that by 2, and remember that £45 for a skirt is deemed "reasonable" by the local inhabitants. Therefore, by dint of my own mental bankruptcy, I am saved from the pain of constant and inexorable guilt, and from any ensuing insanity.
You might infer from this that I'm back in the UK, too.