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 (
    103772, 103771, 103770, 103769, 103768, 
    103767, 103766, 103765, 103764, 103763, 
    103762, 103761
  ) 
  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 0.00045

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 24 Using where

Result

product_id price
103761 1.69000000
103762 1.69000000
103763 1.69000000
103764 1.69000000
103765 1.69000000
103766 1.69000000
103767 1.69000000
103768 1.69000000
103769 1.69000000
103770 1.69000000
103771 1.69000000
103772 1.69000000