As the title suggests, I mean this post as more of a PSA on an interaction I think catches some people by surprise than an exhaustive strategy exploration.
In fact, you could argue this is more of a rules clarification than anything else, but I think it has enough examples/applications to warrant its own post.
With two Quarries in play (or any other way to make Villa cost $1 or $0), gaining Villas becomes a positive feedback loop limited only by the remaining Villas in the supply.
If they cost $1, gaining them consumes nothing, and if they're free, gaining one nets you $1 for the turn.
The only strategic implication I want to get into in the main post is that when these options are available, you can assume the Villa pile will be empty at any given point.
This has some obvious utility for winning on a 3-pile ending, and sometimes enables a "mega-turn," but if we want to get more specific or there are other ways to play around this, feel free to comment below!
I'm sure there's plenty to talk about here that would be better placed in a full-fledged article on Villa, but that's not the idea behind this post, so take from it what you will.