LD4B how good and how rare what are they worth?

What a LD4B is worth is a loaded question. The asking price for them has jumped in the past two or so years. The price of aluminium hasn’t gone up so perhaps there’s a perceived demand increase (or supply shortage)? I upgraded my 318 2bbl to a 4bbl with a LD4B w. 302 heads 3 years ago. My butt dyno says my Scamp feels a lot peppier but I’ve got no proof other than what folks say on the internet with their testing.

I thought $142 (incl shipping) was expensive when I bought mine!