The thing about cheaper dupes is that they're often targeting the *scent profile* but completely ignoring the formula, which is where you hit a wall. You're right that the Walmart and Zara stuff evaporates, but that's not really a dupe problem - that's a concentration problem. Bleu de Chanel is an eau de toilette at 100ml for a reason: it's meant to project reasonably well for the price point. Most mass-market alternatives are cutting corners on both the fragrance oils and the alcohol quality, so they literally can't perform the same way.
If you want something that actually lasts and smells similar, you need to look at niche or indie brands that use better formulations. Dior's Sauvage gets thrown around a lot, and yeah, it's pricier, but the longevity is genuinely there because it's formulated properly. Alternatively, look at brands like Heeley, Maison Margiela, or even some of the higher-end department store exclusives - they cost more upfront but you're getting 6-8 hours minimum, which means you're not reapplying constantly and actually saving money overall. There's also the option of getting an eau de parfum concentration of something similar; it'll last way longer than an eau de toilette, even if it's technically a different fragrance.
One thing I've noticed is that people sometimes buy the smallest size of an expensive fragrance thinking they're saving money, then end up frustrated when they have to replace it constantly. A larger bottle of something decent that actually lasts ends up being better value than constantly buying smaller bottles of something that fades. It's like buying cheap olive oil that's mostly flavorless versus investing in a good bottle that actually tastes like something - the math works out in favor of the real thing.