How much did a rifle bullet cost in 2000?

As much as the retailer charged after their markup. The question is so vague as to be virtually impossible to answer. When you say rifle, you could be talking about anything from a .22 up to a .50 BMG rifle, and even a larger, NFA Class II Destructive Device. On top of there, there are varying loads in different calibers, which will affect the cost, as well.