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 (
    59, 58, 60, 42, 39, 40, 37, 43, 56, 57, 30, 
    53
  ) 
  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 0.00039

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
30 349.95000000
37 159.95000000
39 419.00000000
40 229.00000000
42 79.00000000
43 369.00000000
53 38.99000000
56 220.00000000
57 309.00000000
58 779.00000000
59 599.00000000
60 1499.00000000