Current prices come from TCGplayer’s daily market-price feed (via the public TCGCSV mirror), pulled per set and matched to each product’s exact ID — the same Market Price shown on the product page, to the cent.
The entire TCGplayer feed is snapshotted daily and archived back to Feb 2024. First-of-month snapshots are extracted for every product, giving verified quarterly points for 2024–2025 and monthly points for 2026 — TCGplayer’s own numbers on those exact dates.
Older history comes from PriceCharting monthly closes, computed from eBay completed sales. Every series is validated against the live feed before use, and a spike filter drops lone artifact months. eBay solds running slightly under TCGplayer market is the natural spread between venues.