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 (
    94351, 94332, 93035, 92516, 94682, 92885, 
    94581, 94559, 93751, 94131, 92911, 
    94523, 94521, 94520, 94519, 94518, 
    94517, 94516, 94511, 94510
  ) 
  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 0.00088

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 40 Using where

Result

product_id price
92516 1.69000000
92885 1.69000000
92911 1.69000000
93035 1.69000000
93751 1.69000000
94131 1.69000000
94332 1.69000000
94351 1.69000000
94510 1.69000000
94511 1.69000000
94516 1.69000000
94517 1.69000000
94518 1.69000000
94519 1.69000000
94520 1.69000000
94521 1.69000000
94523 1.69000000
94559 1.69000000
94581 1.69000000
94682 1.69000000