This is a promotion for Battle Born and it plays games. The games notwithstanding, lithium batteries are a more economical long term solution in most cases.
First off, testing exactly to 50% discharge does not reflect typical camper power usage. Camper usage varies greatly, from a few percent some days to maybe more than 50% other days. The usage profile greatly affects battery life and therefor battery cost.
Assuming that 100 Ah meets your daily power needs, what you really want to know is what is my yearly cost of 200 Ah of AGM batteries over their life versus the yearly cost of 100 Ah of lithium batteries over their life.
There are a lot of individual factors in how you use your camper that affect your specific battery cost. What is the load profile of your electrical equipment? Do you have solar or travel daily to recharge regularly? In what temperature ranges do you camp? For one FWC owner who works and camps at a ski resort with temperatures well below 32 F, lithium batteries are useless. If you are 80 years old, the actuaries say both AGM and lithium batteries will likely outlive you. Are you likely to (accidentally) completely discharge your AMGs? I probably averaged 4 years from my AGMs. Other's get 7 or 8 years out of their AGMs. It goes on.