I would say the higher starting pays are proportional to areas with higher costs of living so you have to compare like denominators when comparing job salaries across the country from one nuke plant to another.
You also have to factor in tangible relocation benefits (mine were quantified at 50,000), stock performance, bonus potential, etc.
You also have to compare and contrast all the pipelines from sea to private employment. There is the AUO/NLO path, the instant SRO path, chemistry path, HP, QA, IC, maint, etc.
Each path will garner a different rate based on demand, geographic/demographic, and other factors dripping down from the management bean counters.
My base was over 60K when I started as a chem tech, however I work in Maryland which is expensive. 60K goes further I'm sure in Bumbleville, IA, but I probably would have started at 40-50K there. When I took that crappy job with Tyco as an HP I was brought in at 58K in Missouri and that was salary, and they were a bunch of condecending monkey poops, but I digress.
My current company has performance based step increases within each pay grade and does annual cost of living adjustments, and performance based incentive awards. All in all my base has improved since starting.
I think it all boils down to the person what they make getting out of the Navy and the flexibility to move to where the jobs are and the motivation to do well once there.