This practice does actually exist, and it's called "price anchoring." Before major sales, sellers often raise the price of goods so they can lower it later and show buyers a big discount percentage. It looks like a 50% discount, but in reality the product might not be much cheaper than it was a couple weeks ago.
On Wildberries this is especially common because the platform doesn't track price history in real time for buyers - there's no built-in chart showing how often and how prices change. Sellers know this and take advantage of it. It's especially noticeable before WB fest, when everyone's expecting big discounts - that's when the psychology kicks in: we see a red price tag with a discount and think we caught a great deal, when really we're paying almost the same as on a regular day.
Here's a simple tip: if you spotted something long before the sale, remember the price or take a screenshot. Before the promotion, check whether the discount is actually worth it or if it's just a visual trick. There are also browser extensions that track price history on marketplaces - they help you catch real deals.