Salary Guide for Design/Construction/Real Estate

Dear all,
I received a job offer as a Senior Architect/Project Manager in Lagos. Apart from the full expat package (accomodation, car, insurance, flight tickets) I have been thinking of requesting a monthly salary of 8000 USD. I have been trying to find a guide so as to evaluate the salary to be asked, nevertheless I could not find a comprehensive one. Does any of the bloggers have an idea about the right amount to be requested?
Thank you all in advance for your help.

Start off at a high amount and the company will then make a counter offer. Then negotiate.

Is 8K considered high?