Three examples
What you pay, what's inside.
Decidueye ex Box
Worth opening
+$22
4 packs, 3 promos.
Chaos Rising Booster Box
Not worth opening
−$89
36 packs.
Prismatic Evolutions Elite Trainer Box
Not worth opening
−$75
9 packs, 1 promo.
How
Odds × prices, against the price you pay.
1
Each rarity has known odds
One Illustration Rare in about 9 packs, one Special Illustration Rare in about 90.
2
Each card has today's price
Refreshed every few days. Odds × prices is what a pack is worth.
3
Compared with the cheapest listing
Never an average. If something inside can't be pinned down, the app says so instead of guessing.
Also from Cardlift
A private Discord for cross-grading
Graded cards worth crossing to a better slab, found daily. A small group, opening later this year.