SHIRAZ, aka Syrah, seems like one of those wines, perhaps more than others, whereby if you spend that little bit more, the difference in the quality of the drink rises disproportionately.

Apparently, such a disproportionate rise is the case for most wines.

Wine economists - or vinonomists, if indeed there really are such things - have somehow worked out, using their own theories of course, that on a £5 bottle, 47 pence is spent on the actual wine, whereas in a £10 bottle, £2.87 is spent on wine.

That means that for twice the price, the amount spent on the wine, and therefore the quality of the wine, is more than six fold.

Go as far as £20 - four times the price - and you get as much as 15 times the quality. Apparently.

Using that theory alone - and forgetting the economics found in your own purse - it would therefore seem sensible to pay a bit more and thus get even more of the so-called "bang for your buck".

Now, it might not be wise to bet your bottom dollar on this theory being absolutely correct - plus this disproportionate rise in quality to price is by necessity going to tail off at some point - but it does seem plausible where Shiraz is concerned.

Some of the cheaper Shiraz, especially from the New World, can be like harsh, tangy, headachey, acid soup, the kind of stuff that makes you want to chew your own tongue.

But good Shiraz can be smooth, fruity, fine and with lovely texture.

Currently on offer at Waitrose for £10.99, down from £13.99 until February 16, is The Hedonist Shiraz, from McLaren Vale, Australia, grown biodynamically without pesticides or herbicides.

Full, fruity, fleshy, very dark and silky, and not excessively alcoholic at 14 per cent, it provides plenty of enjoyment and backs up the aforementioned vinonomic theory.

As a minor aside, it also has a splendid modern screwtop that alone suggests quality.

A bit cheaper, and also on discount offer at Waitrose until February 16, is a 2014 Yalumba Organic Shiraz, down from £9.99 to £7.49.

Full of rich red fruit and a nice touch of spice, it doesn't match the Hedonist for pleasure or velvety quality but it's not far behind, while also being a bit more easy going on both the palate and the purse.