I use this calculator to help me determine what size pipe I need for long runs like that. You can play with it to see if you can run a smaller(cheaper) sized pipe for a longer distance before upping it at the source. Then, once you know your pipe requirements, call your pipe source and get a price.
I am about to run a line 2,600' to a new bathroom under construction. The calculator told me I could run 1.5" poly vinyl potable supply line the entire distance with no more than a 3 psi drop. I ordered the pipe in 300' rolls and therefore will only have 10 couplers the entire run. I wanted 1,000ft rolls but worried about handling them. If I were going to run PVC, it would require a 2" supply downsized to 3/4" by the time it got to the bathroom.
Your most expensive aspect with this project will by trenching and wire. Electricians don't like to dig, and I have been quoted as high as $10/ft when they do it. If you can do part or most of the work yourself, you'd save alo of money. I would discourage pulling from your irrigation controller. Typically a controller pulls 3 amps. Five a side and you have a full breaker with no room for drawdown.
http://www.pressure-drop.com/online-calculator