Question [Q] What's the deal with free app space on this phone?

In the HTC Desire days things were easy - I had 300MB partition for apps and if there was 15MB free, it meant I could only install apps that were smaller than 15MB.

But with S4 mini it is not like that. I go to Settings/Apps and it tells me I have 470MB free (which is how much space there is on the internal card), but I can't install any apps (even tiny ones) because of "Insufficient storage available".

What the deuce?
S4 Mini i9195 HTC Desire
[dev] Fast swap on internal (for HTC Desire)