For an active photographer who relies on several key lenses over and over again, the financial argument can be clear. It's cheap when they spread their cost over years of enjoyment. For someone who bought a DA*300 back in 2008, they've still got a lens so good at what it does that it's being sent up in space to use from a modern satellite.
For someone buying sought after lenses, they can actually maintain their value over the years. It doesn't have to be a unicorn like the A*135mm f1.8, it can be the FA Limiteds or Star lenses or Takumars ... these are classics. You can sell them later on and perhaps break even as well as end up with all the great photos taken with them in the meantime. You would need patience to sell them because they are of course niche lenses of a niche brand, but let's say you took a $100 loss after eight years, what it really means is that you rented and got to shoot with that lens for just $12 a year.
And then there are those who are really not photographers, but collectors. The sort of person who decides the K-3 isn't good enough for them, they need to be full frame, so they buy some 24Mp Sony thing and shoot exactly the same scene but with 50mm instead of 35mm to get exactly the same picture.
I shrug my shoulders - what's wrong with LBA in their case? I have middle aged friends who have been into way more expensive hobbies - tinkering with cars, boats, wine collections, even shares in a wretched racehorse (the recurring medical fees!). They've spent way more of their family's income than me.