I only visit places that provide power so batteries are less important to me than those people who camp off the grid. In my case when the sole original battery gave it up I replaced it with two marine batteries from Walmart. Maybe all of $250 with purchase of additional connecting cables.
EDITED TO ADD: two batteries of the original size wouldn't physically fit in my battery compartment so I stepped down one battery size.
former 2008 Jayco Eagle 29.5 RLS
former 2014 F250 6.7 4X4, CC LB