Magic: The Gathering FINAL FANTASY Play Boosters contain cards from FIN and FCA
While this isnt really economic, and Im not 100% sure you can even trade the cards you get from the theme deck, the one theme deck worth getting is the Emboar one
The MTG card count increases multiple times per year with each new release
In the pricier formats, this could involve using proxies to construct playtest decks
Funnily enough, while ETBs continue to drop in price, the booster box is actually on the rise, jumping from around $200 just last week to almost $230 now
Cards like Man-O'-War, Aether Adept, and Venser, Shaper Savant all do a great job at getting stuff off the board, but only in a temporary capacity