That's a very astute question bo. The short answer is, 'More than I think' but I'll try and tackle it.
It's worth bearing in mind that most of my finds are straightforward purchases that don't require anything more than a machine wash and, occasionally a spray with white vinegar and an airing outside. They're the workhorse items, like the Uniqlo merino jumper I found last week or the silk shirt with an unfashionable label. Half the time I don't even mention them because they're not really that interesting.
I talk more about the purchases that are exciting but need a bit of 'aftercare'. If say I've found a wool/tweed jacket or coat and paid £20-£25 (which is more than I used to pay), I'll probably need to spend another £10-£15 getting it cleaned. Increasingly I can do my own alterations but I've learned the hard way that I'm not good enough to alter tailored shoulders so, if that's needed, it could end up costing another £20, bringing the total to £50-£60.
And then there are the duds, which are harder to quantify because of course you don't know at the time that it's a dud. I think I said that at the end of last year, I redonated about a dozen things that I'd bought over the preceding 12-18 months. That was quite sobering as it meant I'd bought a dud about every 6-8 weeks. Most had cost under a tenner but that still meant I'd pissed away £100-£120 in about 18 months. I've been much more careful this year (I hope)!
I've also learnt to avoid going on charity shop 'hauls' as you can definitely get a high from them - well at least I do - and that's when you can kiss your judgement goodbye. So these days, unless I'm away on a trip and can't go back there, I try and stop once I've made that first purchase.
I sometimes wonder what kind of wardrobe I'd have ended up with if I hadn't fallen into these habits all those years ago. I'd have probably spent the same total amount as I tend to spend most of my 'me-money' on clothes. Who knows, I might be sitting on a small, carefully curated and very expensive capsule wardrobe 