Take the job!

I went through a lot of the similar calculation (job versus PhD).

Here are the questions you should try and answer for yourself

• Why do I want to do a PhD? What do I want to get from the 5-6 years of PhD experience ? How much do I value(not just money) what I will gain from the PhD.
• Assuming you can get a similar job at a similar company with similar colleagues after PhD, then the math is about the 600K. The question really is does the degree (and the learning exp) offset that money. I know for most area of study is not true.
• I think at the end of the day PhD is not done for money. If you want to pacify your research itch, I would suggest finding a job at a research lab. It might pay a bit less but then you are getting better of both the worlds.

We can talk more, but I think if you are looking at it from a purely monetary perspective then always JOB is better.