It's not the speed of the bullet that causes barrel wear, it's the higher powder charges required to push the bullet faster. More powder = longer flame time = higher barrel temeratures = more throat wear.
Think of it like welding, when you place the flame to the cold metal, it takes time to heat the metal so you can weld. Once the metal is hot, it takes less flame time to reheat it enough to weld. That's why Catshooter said "If you go to a prairie dog town, all estimates are void (along with the barrel life)". On a smoking hot barrel, you are causing expotentially more barrel damage with each shot.
If it was just bullet speed that wore out the barrel, the wear would be at the muzzle as that is the point of highest bullet speeds.