The quantum of maintenance cannot be measured by any terms.
The maintenance shall be decided after the petitioner proved her claim satisfactorily with substantial evidences convincing the court about her justification in the claim. Also the husband's income, his statement about his liabilities and statutory deductions can be considered by the court provided he provides substantial evidences to justify his defence.
Thus the court will decide only after hearing both the sides and based on the merits on each side.
Your arithmetic calculation or sentimental feelings cannot be considered by court while deciding maintenance.
In any case you may repudiate he claim considering her employment and if there are no children born out of this wedlock, you may not pay any maintenance to her at all.