Recycled lithium might cost 5x more. Not that the disposal cost of a battery is 5x the purchase price.
If the battery pays for its purchase price in 2 years and the disposal cost is 1/2 the price of a new battery (doubt it's anywhere near that), then the it would still pay for the total cost of ownership in 3 years.
From what I understand, used-up lithium batteries are fairly non-toxic and can be safely dumped in a landfill. Still not zero-cost, but probably about as low as you can get. And they can probably recover some of that cost by recycling some of the other metals from them.
If the battery pays for its purchase price in 2 years and the disposal cost is 1/2 the price of a new battery (doubt it's anywhere near that), then the it would still pay for the total cost of ownership in 3 years.