PLAYER - ESTIMATED PRICE Highlighted players are highly recommended, due to a balance of price and ability.
Midfielders:
Server Jeparov - 3,000,000
Ko Kyung-Jin - 1,500,000
Mauricio Pereyra - 4,000,000 (may need to try a loan or monthly installments, but he's definitely worth it)
Defenders:
Kim Jin-Kyoo - 4,000,000 (he may not be rated too well by your scouts, I'm not sure how he's rated elsewhere, but he does an absolutely amazing job at Seoul)
Bashaeer Saeed - 300,000
Kim Chi-Woo - 2,000,000
Nondier Romero - 500,000 (he's good for another year)
Strikers:
Lee Seung-Ryul - 5,000,000
Dejan Damjanovic - 3,000,000
Jung Jo-Kook - 2,500,000
Nathan Delfouneso - Loan
Lima - Loan or 3,000,000
Wingers:
Choi Tae-Wook - 3,500,000
Park Ji-Sung - Loan or 6,000,000 (probably far out of your price range...)
EDIT: These prices are in Australian dollars, and are only an estimate, so it'll be less in most other currencies...