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 (
    124602, 124217, 124737, 124733, 120650, 
    121239, 9672, 123724, 119502, 124103
  ) 
  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 0.00069

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
9672 1.69000000
119502 1.69000000
120650 1.69000000
121239 1.69000000
123724 1.69000000
124103 1.69000000
124217 1.69000000
124602 1.69000000
124733 1.69000000
124737 1.69000000