You are assuming a return of less than 5% and that you do not eat into the capital. Fairly conservative assumptions IMHO. So if you save the $2.5 million you will have more than enough. I have been working on the basis that $1m in today's money would be sufficient for my retirement.
Also bear in mind that $70k is plenty of money when you have no mortgage to pay, no children costs etc. I live on much less than $70k a year and have the costs of two children (soon to be three)
