SELECT 
  cscart_ult_product_prices.product_id, 
  MIN(
    IF(
      cscart_ult_product_prices.percentage_discount = 0, 
      cscart_ult_product_prices.price, 
      cscart_ult_product_prices.price - (
        cscart_ult_product_prices.price * cscart_ult_product_prices.percentage_discount
      )/ 100
    )
  ) AS price 
FROM 
  cscart_ult_product_prices 
WHERE 
  cscart_ult_product_prices.product_id IN (
    74539, 74537, 74536, 74535, 74534, 74533, 
    74532, 74531, 74530, 74529, 74528, 
    74527, 74526, 74525, 74524, 74523, 
    74522, 74521, 74520, 74519, 74518, 
    74497, 74462, 74461, 74423, 73854, 
    73847, 73826, 73625, 73600, 73910, 
    73823, 74413, 74412, 74411, 74410, 
    74409, 74408, 74407, 74406
  ) 
  AND cscart_ult_product_prices.lower_limit = 1 
  AND cscart_ult_product_prices.company_id = 1 
  AND cscart_ult_product_prices.usergroup_id IN (0, 0, 1) 
GROUP BY 
  cscart_ult_product_prices.product_id

Query time 0.00049

Explain
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE cscart_ult_product_prices range usergroup,product_id,company_id,lower_limit,usergroup_id usergroup 13 1 Using where