If $15k gets you a pretty big LFP battery, then you can get hundreds of thousands of kWh of use under gentle conditions like V2G. There are plenty of situations where 2-5 cents of wear per kWh is very worth it.

And if you do replace that battery, and you can't get a huge discount from selling the old one, then slap on a $500 inverter and install it at your house to keep using for the next 20 years.