I have to imagine it comes from looking at the selling price rather than the deal holistically. Without being well versed in leasing, one would expect used/cpo to be cheaper than new.
Can I just get your parents into 2020 Tundra TSS Off-Road (4WD) at $425 DAS and $425 month on 36/12k, please? I would not lease a Used vehicle, to be honest. Or if you have a trade that they quoted $5,000, I can even do $299 DAS and $299 month on 36/12k!
If your desire is to get a truck to modify, you should reconsider if leasing is for you. Those modifications all have to come back off when you return the lease which is going to come up sooner than you realize.
Why is it that leasing used cars is more expensive then new ones? I’ve even put used 2019 ram 1500’s in the calculator and have come up with numbers of $447 a month for a 2019 ram 1500 laramie with 16000 miles at $46000, with all major options except for the black appearance package.