If you were offered £10,000 would you accept that? If not, would you accept £90,000? If the answer is yes to one of those, go either up or down until you reach a figure YOU are happy with.
Look at what other companies are paying for these positions and you should have an idea of what they should be offering.
You also need to take into account:-
where in the world is the job, what country?
what nationality are you (like it or not an Egyptian will get paid less for working in Egypt than say an American would)
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