The money I've spent on buying pins is all pretty much a sunk cost. If they all halved in value I wouldn't really notice, not because I'm made of money but because that money's been spent anyway (at least in my head). The only way to realise the cash would be to sell up completely.
As things stand if machines got cheaper then I'd get less for those that I sold and spend less on buying replacement machines, so no real difference. I'm lucky enough to have bought a lot of my games at cheaper prices but it doesn't mean I've made money unless I sell up and don't replace them with anything.
Once you've got past the initial purchase prices it's a pretty cheap hobby. In the UK you can join a league and play all day at someone's house for less than $4. What other hobbies are that cheap? If I go and see a band then I'm looking at $40-$100 for a day (or evening). Going out drinking would cost me $8 a beer and I'd have nothing left to show for it at the end apart from an expanded waistline and a hangover (And a few good memories hopefully).