Spine surgery still is paid higher than most other things in orthopedics, but their day will come. Slowly, one by one, medicare and others review procedures and look at cost/operative time/etc.... and will start to chop down the spine surgeons as well. So if you are starting orthopedics now, it may be alot different in 6 years when you finish your spine fellowship.
And of course as we've said many times in this forum, don't pick your specialty based on the $$$$, pick it b/c you love it.