What's your real question here? You start off asking what the most interesting subspecialty is and end up wanting to know how much money you'll make.
While both are valid concerns, one (the money question) can be answered fairly easily by visiting the myriad of physician salary websites. Bottom line is that you won't starve but you won't have the biggest house on the block either.
The other (the "interest" question) can only be answered by doing, because what one person loves, another will hate. I love pulling the chains of all the wanna-be stroke docs here, because I pretty much hate stroke (or "vascular neurology" if you prefer). Give me squiggly lines on an EEG or EMG, instead, 'cause I love neurophysiology. If you're really interested in neuro, you need to spend as much time as possible with neurologists in both academic and private practice, in both outpatient and hospital settings. You won't see everything you need to in your one month med student neuro rotation, so you'll may need to put in some after hours time to really do this.
As for "never treating," that's not true as an absolute, but to be honest, there are few slam-dunk fixes out there. Keep in mind that much neurologic disease is chronic and incurable, so your role is usually to treat symptoms and maximize patient function without actually curing. This is not unlike the role of the internist who treats diabetics, hypertensives, etc. If that doesn't appeal, I strongly urge you to look elsewhere.