Choosing Brochure Paper Size

I am designing a tri-fold brochure for a kollel in the US.
They want it to look nice, market themselves well, but don’t want to spend a fortune on it.

I want to choose a standard size paper that US printers carry that will look nicest but not be too expensive.
To me, a basic letter-size tri-fold brochure isn’t classy-looking enough.
I think that square (or close to it) proportions look nicer and more appropriate.

How do I know what the standard sizes are and relative prices?

Is this something I have to ask the client about?
They don’t know yet where they will be printing this.
What if they want me to give a recommendation for a size with a good value or a nice look?

I’d really appreciate some guidance on this or recommendations for a paper size!
Thanks so much!

I would ask the client, he is the one who is paying for the printing. If you want to give him the prices, so he can see it himself - that’s the best.

Thanks for the advice!
I’m in Israel, they’re in the US - where can I get average prices from?

Always easier to find the printer first and check what standard sizes are. For a square brochure probably not going to be standard anyway, especially if you have bleed so anyway will have to be cut down.

Thanks so much for your help!
I told the client to do that, to check sizes with the printer and figure out how much they want to spend…

What quantity are they printing as its important to know f you are limited by paper size or not as a digital printer wont print unusual sizes.
You can always crop down the height of a standard brochure to create a square but doing this with a US letter will create a tiny booklet,
An A3 equivalent may allow for a square trifold but that’s much more pricey to print than a standard trifold and a lot of paper wastage