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 (
    111575, 112163, 111572, 111571, 111570, 
    111569, 111568, 111567, 111566, 111565, 
    111564, 111563, 111562, 111561, 111560, 
    125112, 112045, 112044, 112043, 110706
  ) 
  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 0.00061

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
110706 1.69000000
111560 1.69000000
111561 1.69000000
111562 1.69000000
111563 1.69000000
111564 1.69000000
111565 1.69000000
111566 1.69000000
111567 1.69000000
111568 1.69000000
111569 1.69000000
111570 1.69000000
111571 1.69000000
111572 1.69000000
111575 1.69000000
112043 1.69000000
112044 1.69000000
112045 1.69000000
112163 1.69000000
125112 1.69000000