I would like to know that what is the actual fee for getting an Indian e-Visa online from government portal?
The cost of an eVisa is divided into four blocks - free, $25, $80 and $100, dependent on nationality(all prices in US$). There is a 2.5% bank charge added in addition (Source: Wikipedia)
The Wikipedia page includes a table of eligible countries and notes on which fee applies. It's too long to reproduce here, but iVisa have an interactive page that allows you to select your nationality, and your target currency. Note that their service charge is not applicable if you apply for your eVisa through the government portal
Disclaimer: I have no link with iVisa and neither recommend them nor advise against them. I don't know what their service charge covers. Other agents may well be available.