Booking a "mileage run" (a cheap flight specifically to earn PQP) often provides better value because you get the PQP plus a trip.
Reviewers from platforms like The Points Guy and NerdWallet consistently recommend against buying PQP unless you are very close to a high-tier status like . Cost vs. Benefit
“Zoe said this buy-up offer is worth considering, adding 'This is actually probably less money than if I had taken a mileage run (because of taxes).'” The Points Guy · 1 year ago
Last-minute elite status strategies for United Premier status
Using a United Credit Card can earn you PQP through daily spending (e.g., 1 PQP per $15–$20 spent), which is often more cost-effective than buying them outright. Community Perspectives
Using excess miles to earn status points on United-operated flights.