Can a Book Marketing Service Boost Your Sales?

Has anyone hired a book marketing service and actually seen measurable results? With so many companies offering promotion, social media campaigns, and email outreach, it’s hard to tell which services truly help authors reach readers. Do these services make a significant difference for debut authors, or are they more effective for established writers? I’m curious about real experiences what strategies worked, which didn’t, and whether investing in a professional service was worth it in the long run.