June/July/Aug I usually make it out West a good few times, this year forget about it as you have found out Fares are thru the roof and not worth going. Although I havea Vegas trip planned for Sun costme $153 after a cert was applied, will be there for all of 7 hrs but will earn 6100 EQMs

the purpose of the trip
If U still go U should know PHX has the highest of all airports for Fees,Taxes and Surcharges on Rental cars where Im not surprised when those add up to be more then the cost of the car. Best thing is to find a local rental location and bus it to them or if not far cab it.
if U do go make sure to spend some time in Sedona its off the I-17 which is the hway you will take to get to the GC, also if you have tons of time forget about the GC by Flagstaff and go up to the Northern Rim instead in Utah
Nothing really close Airport wise Vegas is apx 6+ hrs away and ONT/PSP etc are not much better, unless you land and go straight to the GC but that still a very long schelp and alot of burning of gas