N#364090
Hello,
So the above seems to be the item in question & according to the info on it, it appears that you could only get them at a dispenser (I.e. machine rather than a gift shop) inside the church.
It looks like a fairly bog-standard tourist piece, and those machines typically offer these tokens for 1-2€ given what I've seen around the parts of Europe I've visited.
At any rate, I'd suspect it was a pretty cheap & cheerful sort of item.
I hope that helps, or at least gives you a starting ballpark figure.