Dusk , I used to use 5l a week of Lockhills water, which is £1.50 ish vs a zero filter at £15.
However even with London water I’m only now buying another 2 pack, 8 months after my last.
At 4 months each is definitely cheaper than buying bottles, nor to mention the convenience of not having to go out to buy water and not worrying about costs when descaling etc.
thankfully my local recycling centre recycles filters but even without, I still think it’s less plastic than 4 months of 5l bottles.
Spotless is interesting too, but don’t disregard zero filters (unless your stats are crazily high)