Some peak Dou Saints created High-level Heaven-grade Cultivation Techniques, while some peak Dou Saint Ninth-grade Golden Pill alchemists created prescriptions for Ninth-grade Golden Pills. Therefore, the conclusion that a Ninth-grade Golden Pill prescription was more valuable than a Heaven-grade Dou Technique should not be problematic.
In the era Gu He came from, the inheritance of soul cultivation was incomplete. Ninth-grade Golden Pills had not appeared for a thousand years, resulting in a scarcity of top-tier alchemists and a relative shortage of Ninth-grade pills. Things were valuable because they were rare.
Moreover, at the Dou Saint level, Ninth-grade pills had another use besides being consumed: they could be used as grenades. Ninth-grade Treasure Pills were useful even against peak Dou Saints, as could be seen from Hun Tiandi throwing Ninth-grade Treasure Pills during battle. In terms of versatility, Ninth-grade pills were clearly somewhat stronger than Heavenly Grade Cultivation Techniques and Heaven-grade Dou Techniques.
Considering these factors, it did not seem unreasonable for me to establish that a Ninth-grade Treasure Pill prescription was more valuable than a Mid-level Heaven-grade Cultivation Technique.