Why are you set on an investment piece? It doesn’t really make any sense in terms of spending 1k on mid-level high end fashion. Most of the things on sale in there, as mentioned, are either seconds or last season. There are seldom true investment pieces there, and if so they’re reductions are negligible. The common answer of a mulberry bag is absolutely uninspired - despite being a fan, unless you have preexisting notion of the bag or a particular penchant, it serves no purpose, nor does mulberry as a brand carry the same weight. They’re beautiful, but if you hadn’t clocked it before it seems redundant. If you did want to enjoy the experience, spend half of that money going down to london, get a hotel and a really nice meal, and have a genuine shopping experience in Selfridges or your chosen retailer. Or get a personal shopper. So much of the market value of fashion is arguably understanding the weight of the label too, so if that’s lost, why are you spending it at that retailer and to what means?
Also, arguably 1k is not enough to buy a true investment piece in high end fashion, but it depends what your definition of investment is. But if you’re truly talking about “pay per wear” - go shopping without heed to the brand, find what you truly love, will use everyday and bring you joy, and that’s what you should buy.
Suddenly coming into money doesn’t necessarily you should go spend it at once at a place deemed to be of value socially - what will bring you the most joy and value in spending that money? From what you’ve mentioned so-called investment piece is not it. You talk about “A real treat” for you, and yet that is defined not by fashion or trends or advice from people who don’t know what makes you tick. It absolutely does not necessarily fall into line with buying an “investment piece”. These are two different things. You also mentioned that perhaps people might assume that it’s fake as you dress “normally” - then why feign spending a significant amount of money on an industry which isn’t going to bring you proven value? Work our what you want and would make you happy. Good luck!