As much as I really want another Chao Garden, I know the monkey's paw would love to grant my wish. Imagine:
Chao garden. You get 2 chao to start out with. Want to access another garden? $2.99 each. Want more chao? $4.99 per egg. You could feed them the fruit that grows natively in your garden, which raises their stamina slowly, or buy more fruit at $0.99 each. Or buy a fruit tree seed for $9.99, what a steal! Need a pack of tiny animals? 20 for $8.99!
While I doubt SEGA would stoop this low... it's not completely off the table.