There are several 'services' you could use to help you get a visa.
However, as a potentially complicated candidate (born in South Africa, NZ citizen, living in Australia, can't get an ESTA after visiting Iran), applying via the official Indian government visa website was still a reasonably straightforward process.
Unless you have an exceptional circumstance, or other complication, I'd recommend just applying via the government website.
The official site also states:
Services of e-Visa involves completely online application for which no
facilitation is required by any intermediary / agents etc. It is
advised not to believe or fall in trap of any such unscrupulous
elements who claim speedy/express grant of e-Visa and charge money for
The visa fee can change, but according to Wikipedia (Policy of India), the latest cost as of June would be around US$80.