Anyway, if I'm not mistaken, what you're asking is a privilege information. Not because it's HMC but for any organization for that matter. But I'll give you a hint. Similar grade will not necessarily mean you'll receive the same basic salary because there's entry level, mid level, and ceiling. Entry level would be the lowest and may be offered to new hirees and as you 'grow' into the company your salary will be adjusted accordingly depending on your superior.

Why do I know this? I have lots of friends working in HMC. :)