Read the articles in the tacked thread at the top of this forum
Long-range and cheap do not really go together. You've got to pay somewhere.
Given a certain level of "target" ballistics, you then can scale up the terminal capability by increasing caliber (ie, bullet diameter), depending how big of an animal you want to shoot at what distance.
For elk at 1000 yards, I would consider 338LM to be the caliber of choice. That is an extreme distance for hunting.
For more reasonable situations, 7mm WM or RM are a great choice. They'll whack a deer or antelope with no problem to 800 yards.