Costs of Home

...has just hit $3,500 USD. I have not seen my family together as a unit for more than a day or two at a time for more than a year and a half. so we're gonna pay what needs to get paid to get back home. But considering the most we've yet paid for tickets home was about $1,800, this seems exorbitant. What keeps airlines from jacking prices up infinitely? At what price would I be willing to forgo a trip to see family and to get home? Actually, I know: $5,255.50.