why doesn't every country scale up the prices to the international level?
For simplicity suppose the local currency exchange rate is 1 LOC = 1 USD.

Suppose that the central bank simply print out 5 times the paper money in circulation, creating inflation. Pizza would then cost 15 LOC instead of 3 LOC. But then if the exchange rate regime is floating (majority of countries now use this), then the inflated money would be worth less, causing the exchange rate to fall to 5 LOC = 1 USD. That is, you need less USDs to exchange for 1 LOC. In essence, tourists would be paying the same (3 USD, which is now equal to 15 LOC).

So the next question is, why don't the central bank make their local currency appreciate (make 1 LOC = 5 USD, so that the pizza that cost 3 LOC would now be equal to 15 USD.)

Well, the demand and supply for money is what determines the exchange rate. If you want to know more about this I'd suggest you read more on exchange rate intervention here.