Quick take
Waterdrop currently lists the G3 400 GPD combo at $89.97 one-time and about $80.97 on qualifying autoship, but the bundle contents and timing should be matched to the filters you actually need.
Current bundle pricing
The G3 replacement-filter combo is currently listed at $89.97 one-time, with a 10% autoship price around $80.97 on the manufacturer page.
Why a bundle can be convenient
A bundled purchase simplifies ordering and can be useful when multiple cartridges are approaching replacement at the same time.
Why individual filters can still be better
CF, CB and RO stages have different service lives. Replacing a long-life membrane early just to use a bundle can erase the savings.
Best buying rule
Buy the bundle when its contents align with the actual filter alerts and age of each stage; otherwise order only the cartridge due.