If this is via a program where a company buys miles to give out as rewards or whatever, and they're willing to let you buy some (good for them if the price goes down as they buy more), keep in mind that there is usually a limit on how many miles can go to one person in a year. This is usually somewhere around 25,000 miles.

That said, US$250 for 125K miles IS $.002 per point, an incredible price - about a tenth of what their value is commonly estimated as. Intercontinental first class round trips for that price? Where can I sign up?