Sounds like you've done some homework on this.
But I think some careful shopping can get you started with
a "regular" system for as little money if you don't insist
on premium parts, which arent necesary, and you don't pay
thos fish store prices that are unreasonably high.
But the long term cost makes this more expensive than any
other option. The diff in cost might not be realized for
several years if you have only a small aquarium and good
CO2 retention. But if yo have several aquaria or large
aquaria, those refill prices are gonna get you.