E-street vs Promaxx vs 440 Source

Cost of machining was the reason for me to buy Edelbrock heads, rather than more port work on 906 heads. 50 year old castings have already cost me one engine, learned that lesson, as a besides, benefit. 906’s are still somewhat available but, in my opinion, they need hardened valve seats and lots of my time.
I am under the impression that E-street heads have lower budget springs and less durable valve seats, keeping their cost down.