When asking for a salary you should have two numbers in mind: the high end, what you would "like" to get, and a lower figure that is the lowest you will reasonably accept before declining. Hopefully you will end up agreeing on some figure in between.
Salaries vary so much between location, type of job, size and nature of company, industry and many other factors, that it is impossible to say if 70k is "too much" for a starting graduate or not. Some graduates in some situations may achieve that, many others may not. You will need to look at the local job market and comparable positions to get an idea of what is reasonable or not.
When it comes down to it, it's just a number. You have to figure out if it is enough after tax to meet your living requirements for rent, car, entertainment, savings, etc. What you are paid should be a comfort figure, not a prestige figure. You don't want to be taken advantage of, but at the same time so many things count about a job apart from salary, especially enjoyment and the working environment. If it's a good place to work and you like the people, that will compare well to some unknown place that you may hate.