These will be transferred to US Marines in a time of need. That's the beauty of US military from a planning perspective. These are kept in "active reserves" meaning close to new or less than half life used functional equipment, ready to be used in a war.
The embargoed Pakistani F-16's and near 2000 4th and 4.5 generation jets are kept in this category for a WWIII scenario.
Lastly, Pakistan doesn't want to pay even 75% of the price and get into "strings". That money is much better spent on Z-10's and later on some numbers of Z-21's or ATAK's to offset the Apache's. With Z-10, we will truly get an opportunity to create a helo industry in Pakistan like we did with the J-10. In a few years, China will not need them and its manufacturing can be transferred to Pakistan for affordable price.