Installing cost is all over the place and starts at $.75 / ft + pipe here.   Thats why I have my own plow and it takes years for a contractor to show up.   I have gotten some prices on installing 12 in.  $1.60 - $3.80 / ft + pipe.   Boy at $3.80 / ft a old wheel machine could pay for it self fast.   

Pipe prices
4in .35
5in .50
6in .80
8in 1.40
12in 3.65

For your job finding a contractor might be your best bet.  It takes a lot of knowledge and tricks of the trade.  You need quite a bit of work to pay for the equipment.