The old manual still applies because focusing solely on the flight price, even with the best comparators, ignores the economic reality on the ground.
Finding a cheap flight to a country is one thing, but if accommodation, food, and local transportation cost an arm and a leg, the trip will still be out of budget.
Historically, the cost of living on site has always been a dominant factor, much more than the flight ticket alone.
It's like buying a low-cost phone and discovering that the monthly plan is exorbitant; the savings on the ticket quickly evaporate.