Keep in mind that you shouldn't assume that it is a dark or deceptive pattern unless you have solid evidence. In general, pricing strategy is part of the company's business strategy, and price segmentation is a known tactic for operating.
So segment pricing, or price segmentation is a pricing strategy where a company will charge different prices to different segments, based on their perceived value of the product or the ability to pay for it. It does have some benefits including discount for senior citizens or students that we commonly see in many products and services.
There are different segments you can apply, the most common one being customer segments like the much discussed issue about the same product but packaged and sold at different prices for men compared to women.
Then there's the product based segment you see in many SaaS products where there are a number of tiers or packages you can choose from. The free or freemium tier is targeted towards acquiring new customers and the premium tiers are usually for customers that use the product and want more features.
Location pricing is as the name suggests, varying the pricing based on the location of the customers.
Time pricing is a pricing strategy in which prices are adjusted based on the time of day, day of the week, or other factors that create a perceived shortage in supply or urgency for the customer to take action.
There are often legitimate reasons why businesses may price their products differently, but I would only suggest that it is a dark or deceptive pattern when it is a purely profit driven and misleading pricing on the products (e.g. selling the same product with less quantity at a higher price but claiming that it is the same quantity at a lower price).