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 (
    8862, 8860, 10172, 8878, 8861, 10076, 
    10945, 8864, 9848, 8880, 8875, 8869
  ) 
  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 0.00044

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 13 Using index condition; Using where

Result

product_id price
8860 849.000000
8861 1042.000000
8862 1016.000000
8864 1391.000000
8869 3791.000000
8875 2154.000000
8878 0.000000
8880 1799.000000
9848 302.000000
10076 1368.000000
10172 2500.000000
10945 1016.000000