Define "luxury items". Are you talking something that's high quality, or something that has a "recognizable label" on it that you are buying because of the "recognizable label"?
Also, what do you consider "well off"?
For the area I live in; I'd be considered "upper middle class" as I'm above 75% of the income for the area I live in; and I live in a decent well maintained house in a working class rural community. But I still have (a very reasonable) mortgage and I drive a nearly 10 year old Subaru Forester and not a Lexus or a Benz. (There are people in this area who have Mercedes. I'm just not one of them. Not that I couldn't necessary afford one; they just aren't a brand of car that has the maintenance record I'm interested in!)
I'm all about: "What's the best bang for my buck?" Which is Scriptural. Being a good steward of your resources is Scriptural!
Personally, I like to mix and match my own creative flair and I look for things that are well made. I wouldn't call the manufactures I generally buy things like clothing from "luxury" though. I buy from manufactures like Brooks Brothers, some Free People, Anthropologie, and Banana Republic items. Some shoes from Clarks, Born, Birkenstock or Ugg. Clothing and accessories from Chaps, Coach, Shukr, Haute Hijab, Kate Spade, Barbour, Paula Nash, Spyder, The North Face, Pagoda etc and I have lots of Lanz of Salzburg flannel PJ's. LOL - But I don't know too many "well off people" who'd call those "luxury brands".
I also tend to hold onto stuff for a long time and use it till it wears out! I have a fair amount of clothing. But I don't cycle thorough stuff very quickly because I'm quite picky and won't buy an article unless I really love it. I don't make quick decisions when considering stuff that's "non-consumables". And even when I'm buying groceries, vitamins, and services like health care; I'm still looking for "best bang for my buck".
And as a result; we are generally healthy and comfortable.
I do have a few things that are pricier like Eileen Fisher, Burberry, Frye, and Tori Burch. Also I've found some nice leather, and fur coats / jackets that are well made; but I honestly don't know if they are "luxury label" or not? Some of the labels on that type of stuff; (fur and high quality wool coats) I've never looked up. (Found them in consignment shops.) I did recently snag a pair of "gently loved" Golden Goose sneakers off of Poshmark for $250. But I bought those because I've heard lots of people I watch on YouTube say they are the most comfortable sneakers they've ever worn. (I do watch "slow fashion" "influencers" on YouTube.) (And Golden Goose sneakers are comfortable. I'd buy another pair of them; I just wouldn't pay $600!)
I'd also be interested in trying something like a Gloria Bearden blazer or Mosey jeans. My kitchen is filled with brands I've found at Williams Sonoma and much of our linens came from Pottery Barn; but personally, I have no interest in something like Coco Chenille, Gucci, Prada or Louis Vuitton. Only shopping I've ever done in places like Nordstrom's or Sacks 5th Ave is on the clearance racks in their outlet stores and I've NEVER bought anything in Neiman Marcus. I actually think it's entertaining to go in there and giggle at the outrageous prices!

$3000. for a denim shirt someone hand stitched ostrich feathers on? Now THAT'S funny!
I think it's silly to pay that much money for stuff that half the time isn't well enough made beyond the price of things I'm already buying. The real cost of quality can only go so high. Beyond good quality; you're just paying for "fluffy names" someone slapped on a product.
I do like interesting and unique things that are well made. But $6000+ for a purse is silly because in the end; this earth and everything in it will burn up. I'd rather spend $2000 on a sewing machine and make my own "up-cycle styles" than pay thousands of dollars for someone else's name; whom according to Scripture their items will just come to dust and they themselves will probably end up in the Lake of Fire! That's the best Scriptural argument I have against paying that kind of money for just "stuff".
Like I've said; I do appreciate well made items; but I don't pay full price for anything either. I buy "higher end" things off Poshmark, eBay, ThreadUp or The Real Real. I've even found decent stuff at the GoodWill and consignment shops. Most of my Coach and Kate Spade stuff came from 2nd hand stores. And I've bought mostly gold and silver jewelry from estate sales and small "mom and pop" antique stores. I like checking places like that out. They often also contain good history lessons!
But for me, the real adventure is in finding the deal; not necessarily "the name" and of course never spending retail for anything!
So if that's what you mean by "luxury items" (well made things); no, I wouldn't say that's "sinful"; particularly if you are using these items "up" and not wasting them. I also don't "buy trends" because they are trends. I'll buy a "trend" that I really like and will wear whether it's "in" or "out"; but I would not say I have a "typical wardrobe" either. I have a rather "artsy" style of dress and a lot of unique items.
But if you're buying "names" to show off the "name" then it might be worth asking yourself "Why am I doing this?"