Yeah, the investigation writes itself. Have a few people with widely verying demographics come in and buy the same things, compare prices and see who gets overcharged for what. If you work for a news agency publish the findings. If you don’t, post a blog and make memes.
Ideally, this would eventually lead to state micromanagement of price regulation the way some food staples are, but on everything. Or a new wave of anonymous shopping.
If you’re good at it you can teach a course.