RICHARD: It costs a fortune to travel first class in Europe. We only do it every two years
EMILY: In the fall.
RICHARD: It’s just not in the budget this year.
Richard and Emily didn’t go to Europe the previous fall, so they would normally have gone this fall, except that it’s not in the budget. Most likely that’s because they are paying for Rory’s schooling – a year’s tuition at Chilton would be enough money for two first-class vacations in Europe. (Of course the idea they could have a cheaper holiday is one they can’t get their heads around, and they wouldn’t enjoy it anyway).
Richard and Emily are extremely tactful about this shortfall of money, even after Lorelai and Rory keep cluelessly pushing them on the issue. Think how easy it would have been for them to snap (or even state calmly), “We’re not going to Paris because we need the money for Rory’s education!”. It’s to their credit they never make Rory feel like a financial burden, and are quick to reassure her if someone else tries to imply that she is.