I heard that buying a ticket from a different country (like using a VPN to access the website from another country's IP) may change the price. Is it true? Any specific Airline or example that I can try this?
Airlines do sometimes publish fares that are different based on the "Point of Sale" (POS), which basically refers to the country in which the ticket is purchased.
As an example of why they do this, consider flights between the US and Australia in July. July is summer in the northern hemisphere but winter in the southern hemisphere, so there is likely to be more demand from Australians visiting the US at that time of year than there is people from the US visiting Australia. As a result of this demand, the airline may choose to increase the price of flights for Australians (who are more likely to pay them as they are headed to summer!) and keep the price the same for Americans who would not be willing to pay the higher charges.
So yes, this does happen. Not always, but sometimes.
So the next question is how can you make use of this? The simple answer is that it depends on the airlines involved.
Sometimes simply using a travel agency in the country you want to book from is enough. That could be a physical travel agency (eg, via phone/email), or an online travel agency. Sometimes you can use the local website of the airline that you're wanting to book, or even just their global website but changing the country selection on the website (eg, United Airlines has a dropdown box on their website to select the country).
In general there's no need to be seen to be in the country that you're booking from, so generally no need to use a VPN - although it's certainly possible there are websites out there that do require this.
However as you can imagine, airlines generally don't like you doing this as it costs them money! As a result, over the past few years they have started taking action to stop this from happening. Travel agents that repeatedly exploit this loophole have received warnings to stop doing it (and can potentially be "fined" by the airline on the basis that it is normally against their agreement with the airline to make such bookings).
Many online travel agents and some airline have added additional checks to stop people abusing this loophole. For example, when booking a ticket on the United Airlines website, if the country your credit card is from is different to the country you're claiming to be from, then it will re-price the ticket using your credit cards country. Unless you have credit cards from multiple countries, then it's not possible to book these flights via their website!
Also if your credit card has foreign transaction fees, you will need to factor these into the price - you're going to be charged in the foreign currency so you'll be hit with a conversion fee (often 3% or so) unless you have a payment method that doesn't charge such fees.
As far as finding such "deals", the ITA Software "Matrix" tool will allow you to set the "Sales City" which will act as the point of sale (You can also set the currency, which will affect only the displayed price and NOT the point of sale).
For example, using that tool for a flight from Australia to the US in July as mentioned above, the flights between SYD-SFO-SYD for some random dates costs US$1,976 if purchased in "Sydney", but only US$1,738 if purchased in "San Francisco" - so in this case someone from Australia could save US$250 booking on the US site rather than the Australian site (presuming, of course, they could find someone in the US that would actually sell them the ticket - the United.com website would not!)
Yes, but it's hard. Eg for a while on Flightfox when you had flight hunters (not part of their system any more), one trick was to look for flights on Brazil sites, as their taxes were often lower. However you needed a national ID and some other complications.
I run Beat That Flight in Australia and have seen OTAs (online travel agencies) show different prices to what is shown on say Jetstar NZ's website, because it doesn't take into account Jetstar Australia's sales. OTAs can see both, and can find the discounts.
Furthermore, sometimes, say, Qantas/Virgin in Australia might have a discount code not eligible for their overseas websites.
Hard to give an example because prices always change, but the most common discrepancy is on Jetstar on Fridays, when either the AU/NZ sites run their "Friday Frenzy sales" and sometimes by combining the two on a 3rd OTA website found via my site, I can beat both their official prices combined.
[We had a similar question 4 years ago where I tested with a VPN and couldn't see a difference, but that was just with one example. There may well be other sites/places where it does happen)
I have personally experienced this when travelling in Asia. I was using 3rd party booking service. The service also handles flights, but I was looking just for hotels at the time.
If my phone was connected to wifi, the prices were cheaper than when my wifi was turned off. With wifi the IP comes from local country, and without wifi data roaming shows my IP coming from Europe.
But this of course depends on the service you use, and their pricing model.
The POS (or PCC) can not only show different fares but also show different availabilities.
For example, before Alitalia (the Italian flag carrier) was rebranded, you could only see + book the lowest available fare class for all flights from the U.S. to Italy with an Italian PCC, not with any other European or U.S. PCC. Same when flights are almost booked out, you can still see better availability with another county PCC. As a rule of thumb, you should always check the origin and destination PCC to get the lowest price. The easiest for regular users is to just browse the both the departing and arriving kayak & expedia website. So lets say you wish to fly from the U.S. to France. Make sure you check kayak.com, kayak.fr, expedia.com and expedia.fr
Airlines also regularly misfile fares that go beyond the radar because its for country PCCs that none of the usual OTAs book with, those go unnoticed.
Here is what I'm doing. I have access to more than 50+ different PCC around the globe. When I'm booking something I don't have to check manually each PCC since this would take forever. Instead, my system checks each PCC individually and returns only the ones that are cheaper. My system then 'learns' which PCC are usually the cheapest and over time does not check the PCCs anymore which didn't have a good price since each search costs quite some $$ I then use another system to predict if the price will go up or down (using historical pricing + cached data) and if the ticket should be instantly issued or wait until the ticketing time limit is reached.