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 (
    10353, 8869, 526, 10355, 8886, 10211, 
    10222, 8870, 8868, 10173, 10223, 8887
  ) 
  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 0.00052

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
526 1276.000000
8868 1882.000000
8869 3791.000000
8870 3791.000000
8886 4310.000000
8887 4310.000000
10173 1584.000000
10211 2986.000000
10222 1543.220000
10223 1831.780000
10353 1460.000000
10355 1360.000000