Do AIs reply with numerous em dashes to save money somehow?

No. For hundreds of years authors loved to use the em dash. It was a sign of quality writing. Only very recently has it stopped getting used and only because the - is on the wrong side of the keyboard and it's becoming more a hyphen instead.

When someone uses an em dash, it implies they arent using a normal keyboard; not even dvorak.

It's being speculated it's because of RLHF where the humans are from some place in the world (don't remember which place) there they use emdashes.

I don't know where the recent idea that em dashes are difficult to type came from. MS Word automates turning a hyphen into an em dash as you type in the same way that it converts "teh" into "the" and has done so for as long as I can remember.

I find the whole AI / em dash thing frustrating as I used to used them all the time. They have meaning that hyphens don't. I've now had to stop using them because they are seen as AI generated, and structure my sentences differently as a result.