I was able to confirm with Alaska that the Price Guarantee is going away.
Our alaskaair.com price guarantee is going away for tickets bought on or after September 1, 2018. We will continue to offer our price guarantee for guests who find a lower fare on another website within a day of purchasing a ticket (at least $10). We’ve seen relatively low usage of this program over time and it is a time and resource intensive to process requests. Alaska is still a really generous airline and we have 20% lower fares on average than the legacy carriers.
The exception to this is that we’ll continue to waive the fee for Alaska Mileage Plan elites (MVP Gold and MVP Gold 75k) who make changes to their tickets.