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 (
    104473, 104472, 104471, 104470, 104469, 
    104468, 104467, 104466, 104465, 104464, 
    102273, 102272, 102271, 102241, 105014, 
    104448, 102207, 105000, 104893, 104892
  ) 
  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 0.00100

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
102207 1.69000000
102241 1.69000000
102271 1.69000000
102272 1.69000000
102273 1.69000000
104448 1.69000000
104464 1.69000000
104465 1.69000000
104466 1.69000000
104467 1.69000000
104468 1.69000000
104469 1.69000000
104470 1.69000000
104471 1.69000000
104472 1.69000000
104473 1.69000000
104892 1.69000000
104893 1.69000000
105000 1.69000000
105014 1.69000000