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 (
    27405, 28091, 39342, 113610, 123944, 
    124180, 124301, 25405, 27370, 27773
  ) 
  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 20 Using where

Result

product_id price
25405 1.69000000
27370 1.69000000
27405 1.69000000
27773 1.69000000
28091 1.69000000
39342 1.69000000
113610 1.69000000
123944 1.69000000
124180 1.69000000
124301 1.69000000