Same card or different cards?
The per-card price depends first on whether you want copies of one design or a set of different designs. Copies are cheap because they print as a single run; different cards cost more because each one is its own design.
A Bulk Box is copies: $37.99 for 25 ($1.52 each), $64.99 for 50 ($1.30 each), $89.99 for 100 ($0.90 each). A Rookie Box is different cards: $17.99 for one, down to $49.99 for eighteen, about $2.78 each.
Fill the box before starting another
Within a Rookie Box, every card you add lowers the average. Two cards are $21.99 ($11.00 each), five are $31.99 ($6.40 each), ten are $43.49 ($4.35 each), and eighteen are $49.99 ($2.78 each).
Two separate one-card orders cost $35.98; the same two cards in one box cost $21.99. If you are making cards for siblings, a friend group, or several seasons, one box is the cheaper route.
Teams
A team pack, ordered through a coach's team link, is $29.99 per player for 26 copies of that player's card (25 standard, 1 holographic). That is about $1.15 per card, and the team earns on each pack ordered through its link.
Shipping changes the math on small orders
US standard shipping is free on orders $30+ and $5.00 flat below that. A one-card order at $17.99 pays the flat rate; a five-card box at $31.99 does not. On small orders it is worth adding the card that crosses the line.