The cheapest option is the military route however the military is very selective and pilot positions are very competitive. Once your military commitment is over, you will be in a very good position to get a job with any major airline. They love military pilots.

As far as the civilian route goes, being a graduate of a big aviation university really does not help you much towards your final goal. It also ends up being the most expensive.

Personally I would get a degree in an area of study that interests you and pursue your flight training at a decent flight school nearby. That will help to keep the cost down.