If he wants to try bowhunting one more year, before going X bow........how much is that worth?

It's not just an investment in gear.

It's about living.

And the price to do what he wants, is totally up to him.

IMHO bows depreciate bad enough, no bow is an investment.
Some are better than others at holding value.

Paid 980 for my Blackwidow new, shot it a ton, won some shoots, killed deer and when injury forced sale (had to go back to compound for a bit).........sold it for 600.
Quiver and arrows too.

So it "cost" me about $100 a yr to shoot a custom built bow................man that was a friggin' BARGAIN!