SELECT 
  cscart_product_prices.product_id, 
  MIN(
    IF(
      cscart_product_prices.percentage_discount = 0, 
      cscart_product_prices.price, 
      cscart_product_prices.price - (
        cscart_product_prices.price * cscart_product_prices.percentage_discount
      )/ 100
    )
  ) AS price 
FROM 
  cscart_product_prices 
WHERE 
  cscart_product_prices.product_id IN (
    60005, 60004, 60003, 59483, 59482, 59481, 
    59480, 59479, 59478, 59477, 59476, 
    59475, 59474, 59473, 59472, 59471, 
    59470, 59469, 59468, 59467
  ) 
  AND cscart_product_prices.lower_limit = 1 
  AND cscart_product_prices.usergroup_id IN (0, 1) 
GROUP BY 
  cscart_product_prices.product_id

Query time 0.00067

Explain
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE cscart_product_prices range usergroup,product_id,lower_limit,usergroup_id usergroup 9 40 Using where

Result

product_id price
59467 1.69000000
59468 1.69000000
59469 1.69000000
59470 1.69000000
59471 1.69000000
59472 1.69000000
59473 1.69000000
59474 1.69000000
59475 1.69000000
59476 1.69000000
59477 1.69000000
59478 1.69000000
59479 1.69000000
59480 1.69000000
59481 1.69000000
59482 1.69000000
59483 8.99000000
60003 1.69000000
60004 1.69000000
60005 1.69000000