I can’t provide you with data, but there’s a wide range in specialist salaries…I’m in pathology which is one of the lower paid specialties, and I don’t really make any more money (maybe slightly more) than an urban GP would. I started around 120k and I think an entry pathologist at my company would start just below 130ish now. I do extra cases and make more than that but not everyone in my company does. What being a pathologist does allow me is freedom to work remotely and pretty much set my own hours. A few months ago I was able to move to a rural area and my salary is much higher than average for the area and goes a lot further.
I have friends in private specialty practice (IM, Onco) that were expecting high 100s, low to mid 200s for a four day workweek. Surgeons maybe on the higher end. I’ve heard radiologists often make more (200-even 300) in private practice but that is a specialty where you can make a lot more by working more. Derm and cardio are very in demand so I would assume they’re on the higher end. I don’t think there’s much of a financial difference between non-boarded ER vets and criticalists except the criticalists usually have better daytime shifts? So yes, in general you’re going to come out with a higher salary at the end of a residency but it’s quite variable between specialties. It’s probably “worth it” in that you can afford to delay loan payback three years and then more aggressively pay them once you’re done. Edit: if your goal is academia expect salaries more like 120-150 across the board.
BUT
Specializing is a long tiresome and thankless few years and if you’re just in it for the money you may struggle to remain invested in the process. If you don’t love what you’re specializing in the hours spent reading thousands of articles and textbooks and seeing patients can become arduous (and even if you love it it can be too). Specialize because you truly love the subject and enjoy the higher salary for your efforts. But don’t just pick a specialty because it pays well.