This is just going off of memory form last Fall, but here are the major costs to do it yourself.
4-5′ Window Well $199.99 @ Home Depot.
Anderson Casement Window $189.00 @ Menards (Screen comes Seperate)
I borrowed the saw from work and had the Maul.
2×12 Treated Wood Material for the wood bucks $25.
Misc Hardware & Caulk $20.
The rest of it is your elbow grease. Anyways I bleieve I put that window in myself for under $500. I also had to remove some patio when I did mine. Like Watson said digging the hole is the hardest thing. Do it yourself and use the money you save to buy more fishing/hunting stuff .
Just remeber to check down@ city hall for any special requirements that the city may have. Depth of grade to bottom of pit (if you go over a certain depth a ladder may be required, I believe in my town it was that anything over 44″), bottom of pit to basement floor, opening width of window, etc.