The value of these properties keeps going up so PSE will have to pay more and as oil rises & PXD's stock price keeps going up even faster than the value of the properties b/c of all of PXD's leverage.

It is in the interest of both companies to get the deal done ASAP. So, PSE can pay less money and PXD can get the money in soon to repurchase stock now (before the recovery) when the repurchase will do the most good.