Could you explain the criteria you're using to state the access to the passive infrastructure is 'very cheap'? I believe it's at a similar level to the same products elsewhere.
Openreach PIA (duct and pole access) is very cheap when compared to the cost of digging your own ducts or installing your own poles.
What do you mean by "the same products elsewhere"? There isn't really anything that competes with Openreach PIA in the UK. Or are you comparing with other countries - if so which ones?
On dripping with money, etc, of course altnet build is being done with an eye on being potentially acquired. You didn't think CityFibre and VMO2 were planning on hitting their coverage ambitions just by building their own networks, did you? 
Certainly that's how Cityfibre are building today, with a few exceptions (e.g. acquisition of KCOM national backbone).
The problem with buying up a hodge-podge of tiny altnets is that they are all built to different standards and with different equipment, making them very hard to integrate into a unified wholesale offering.
I expect eventually there will be a fire-sale, and someone will buy up the assets and try to do something with them, but both CF and VMO2 need to be building stuff *now*, not waiting for the bubble to burst.