I would note crucially that "point transfers" are often used as the basis for promotions.

Many airlines allow points to be transferred but the cost of the transfer is often close to or even greater than the value of the points themselves. In these cases, point transfers are almost pointless (no pun intended).

For example:

USAir allows points to be transferred for a fee of 1 cent per point, plus 7.5% tax, plus $30. So a 50,000 point transfer costs $567.50.

However, last fall they had a promotion where for every point transferred out, the recipient got two points. So if you transferred 50,000 points, you were in effect buying 50,000 points for $567.50.

Delta has had similar promotions, although I don't know if their bonuses have been as high as 100%.

So to say "USAir charges 1.075 cents per point plus $30" would be accurate when they don't have a promotion, but someone reading this "definitive" thread could be easily misled if they do have a promotion at some point.