OK, thank you. Enlightening as always....
It is a matter of quantity supplied to effect the market price of a fungible commodity, be it gold, oil, wheat, etc.
Produce an extra bushel of wheat, no change in price.
Produce an extra billion bushels of wheat, and the price is going to drop.
The Keystone XL pipeline would not significantly change the market; it doesn’t produce more oil by itself. But it does make it more cost effective to increase production by others.