Countryside Pearl gain started at 8P for the first 70Lv, then 24P forLv71-140, 41P for Lv141-210, 57P for Lv211-280, 74P for Lv281-350, and continues to increase incrementally every 70Lv. The rapid Pearl gain, as well as the massive WP gain from the Country Girls, makes this area the best place to farm both of those things.
Side note: When trying to earn Cash, have Ms. Rack dance at the Auditorium(if you've summoned her, that is). She has the most raw Talent for it. Then you bring Campus Loyalty to a high level, go back to the Auditorium, click Change, and click Ms. Rack again. The amount she earns should go up correspondingly to the Campus Loyalty. Every 1000Lv should allow her to earn 500k, and it stacks. At Lv3000, she brings in $1.5M+, which is easily enough to upgrade Buildings and store-bought Power-ups. After a Reset, she continues earning the same amount of Cash, even though Loyalty has been reset to 0, until you try to change who's dancing, then it goes back to Base Value.