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 (
    575, 505, 574, 599, 10072, 572, 1189, 
    1155, 1157, 1161, 1166, 577
  ) 
  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 0.00070

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 product_id 3 12 Using index condition; Using where

Result

product_id price
505 105.760000
572 43.900000
574 31.010000
575 54.420000
577 19.930000
599 32.910000
1155 27.070000
1157 60.000000
1161 26.470000
1166 75.000000
1189 9.820000
10072 81.730000