Domcomp - No-nonsense domain price comparisons, updated daily
TLD List - Compare Prices of All Top-Level Domains
Savings.com - Compare prices at local stores & discover the best deals
Tldes - Comparison of domain prices of 86 registrars. Data is updated every 4 hours.
PriceCute - Keep up with your competition's pricing on Amazon
The Mac Index - Compare Apple product prices in different countries