70 lakh (7 million) rupees or about $116,000 is the spending ceiling for each parliamentary candidate in India’s election. With an average of 1.5 million voters in each constituency, this translates to an expenditure of about 8 US cents per voter, though some candidates are thought to spend several times more than allowed, without declaring it. According to the Association for Democratic Reforms, the average campaign expenditure by candidates in 2009 was 14.5 lakh rupees (pdf, p. 12), or 1.5 US cents per voter. In the US, candidates in both the congressional and presidential races can expect to spend several dollars for each vote they win.
Source: How India Lives, a company founded by journalists, which seeks to increase the access and search of public data in India. More statistics on the largest election in history here.