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 (
    73240, 73116, 72858, 72857, 73405, 73404, 
    73403, 73155, 73115, 73351, 73350, 
    73349, 73348, 72836, 73284, 73111, 
    71691, 68825, 49338, 44239, 44238, 
    42033, 73271, 73270, 73252, 73239, 
    73237, 73217, 73156, 73119, 72856, 
    72855, 72852, 72032, 71703, 71486, 
    71485, 71484, 71483, 73020
  ) 
  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 0.00066

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