Why swords are so expensive?

[gilbertocarlos]

If you see the prices of knives and swords, there is a huge increase from large to long knife, and from long knife to shortsword.
Dagger - 0,25lbs - $20
Small Knife - 0,5lbs - $30 - Increase of 50%
Large Knife - 1lb - $40 - Increase of 33%
Long Knife - 1,5lbs - $120 - Increase of 200%
Shortsword - 2lbs - $400 - Increase of 233%
Thrusting Broadsword - 3 lbs - $600 - Increase of 50%
Thrusting Bastardsword - 5lbs - $750 - Increase of 25%
Thrusting Greatsword - 7lbs - $900 - Increase of 20%

As you can see, there is a huge increase in price from large knife to long knife, and from long knife to shortsword.

What's the reason for the huge increase? do storical prices follow this logic?

Wouldn't be better to either increase the prices of knives, and the LT/B prices be considered for cheap knives, or instead, decrease the price of swords, and the LT/B prices be considered for fine swords?