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 (
    69744, 70160, 70124, 70080, 69934, 70084, 
    70083, 70079, 70078, 69981, 69817, 
    69729, 69623, 70081, 69727, 69777, 
    69979, 69906, 69874, 69504, 69983, 
    68700, 69905, 69574, 69826, 69754, 
    69825, 69468, 69755, 69753, 69614, 
    69548, 68699, 69704, 69703, 69700, 
    69699, 69347, 69318, 69619
  ) 
  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 0.00044

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