Is it really necessary to pay for another pay card when traveling to a different country?

Is it absolutely necessary? No. Plenty of people do travel internationally without it and never have a single issue.

Is it a very good idea to have one? Yes. Experience has taught many that this can help a lot.

Think about it like insurance. Yes, in the vast majority of cases you are paying and not actually using it. But the day something happens, things go a lot better if you have it (and the right one).

There are many possible alternatives/mitigations. People travelling as part of organised group tours will often have a lot less needs for money while abroad for instance, and have staff or fellow travellers who can assist in case of an issue. Or you could bring cash and carry it with you in a safe place (different from the place where you have your card).

In some places (though they are becoming exceedingly rare) any card at all is even useless, and cash is king.

But if you travel by yourself, to the average tourist destination, and don’t like carrying lots of cash or even having to convert money before you leave, then yes, having a second card is a very good idea.

It’s happened to me a number of times to arrive in a new country, go to the first ATM I find in the airport to withdraw some local money (for taxi or public transport or whatever needed cash at the time) and find the first card used to be blocked for whatever reason. You’re just happy to have a second one then.

Likewise, paying in a restaurant or shop and getting the infamous “declined”. Not fun if you don’t have another card.

I’ve even had the case (back when imprinters were still a thing) that a restaurant broke the card I gave them by placing it incorrectly in the imprinter.

Yes, even if you tell them in advance, cards can be blocked, and no, you can tell them whatever you want, they will not switch off their security systems which get triggered by seemingly random events.

Even if the card is not blocked, there can be other issues like outages (yes, those really happen) or the card getting damaged.

Also, it is important to remember that many cards just won’t let you withdraw/spend all the money you want, even if you have it on your account. Many have limits per day or week or month, and they are often different for withdrawals v. payments and domestic v. foreign. Some of those limits can be extremely low, so double check before departure.

Again, you may make an entire trip and never use that second card. But you’ll be really glad you have it the day you need it.

"bring at least two different pay cards from two different banks" when traveling to a different country. To me, this sounds like insanity.

When I arrived to La Paz on New Year Eve late at night a few years ago, the ATM ate my Revolut credit card at my first attempt to get some local cash at the airport before getting to my rental car. The bank owning the ATM was closed. Currency exchanges shops were closed. My second credit card helped me avoid sleeping hungry at the airport or having to beg around. Not having a second backup card is doable but can make bad, admittedly rare situations much worse. Up to you to make the call.

Note that $6/month is rather negligible compared to be various banking fees you'll likely get when using the card (typically, bad currency exchange rates and foreign transaction fees) or other travel expenses. Also, in many countries, $6/month is a bad deal: many cards are free nowadays.

It is a good idea to have more than one means of payment when traveling. Cards do get shut off sometimes, yes even if you notify them that you're traveling, and the middle of a trip when you urgently need to pay a taxi driver or board a train is not a fun time to be trying to make international phone calls to your bank to sort it out. Having redundancy is a good practice.

But it shouldn't be necessary for this to be expensive. Much of this will depend on the banking situation in your country, which you haven't told us. Where I live, many credit cards have no fee (or those that do offer additional benefits in exchange for that fee, so you can decide if a card with an annual fee is worth the benefits), and there are a variety of no-fee debit card products available if you look around.

We don't really do product recommendations here, and we don't know what country you're in to even know what options you might have, but I'd search for no-fee credit and debit cards to see what's available where you are. Some people here like Revolut, if you're resident in a country they support.