At most the host city will benefit from some upgraded infrastructure, probably long overdue, but very rarely will the host come close to recouping the cost they have put in, and a lot of the money goes to waste, meaning that if they had spend the money purely on improving their citizens live, it would have gone much further. Supporters counter this by saying that the host will get more back in the long term from business promotion and tourism, but this claim is dubious at best, but being a very hard thing to quantify it's also impossible to refute, but considering it's mostly held in cities that are already some of the most popular tourist destination and business hubs, it's hard to see what real difference is being made.
At the end of the day, the Olympics have very successfully branded themselves as a must have event, however the only ones who really benefits are the sponsors who gets a venue where a country's normal safeguards and laws are completely nullifies, the politicians who get to stand on the grandest stage of all and proclaim how awesome they are and the of course the members of IOC who gets to take home fat bribes.
Again, fuck the Olympics. The great white elephant of the modern age.