[copperwater69]

Landscaping boulders near me are $260 a tonne. How do these brothers afford the stone or placing of finished stone?

Here's nice footage of a big ol' stone CNC.

https://www.youtube.com/watch?v=iI8OmfEK8cE

[throwaway4aday]

If you're buying rock from a landscaping business, you're paying retail. I would think they'd buy directly from a quarry.

[lsaferite]

Looking at their monastery location on Google Maps, they very well might have their own quarries.

[williamscales]

And given they're monks, if the quarry owner is Catholic they might get an especially good deal.