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 (
    10206, 10713, 9824, 9871, 9826, 396, 
    713, 10208, 556, 9854, 9825, 705
  ) 
  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 0.00045

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 product_id 3 12 Using index condition; Using where

Result

product_id price
396 5046.000000
556 1063.410000
705 95.000000
713 220.000000
9824 1960.000000
9825 1377.000000
9826 1628.000000
9854 0.000000
9871 1435.000000
10206 4097.000000
10208 4702.000000
10713 0.000000