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 (
    88200, 88199, 88198, 88197, 88182, 88181, 
    88180, 88179, 88178, 88177, 88176, 
    88175, 88174, 88139, 88324, 88043, 
    88042, 88041, 88040, 88038
  ) 
  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 0.00071

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
88038 1.69000000
88040 1.69000000
88041 1.69000000
88042 1.69000000
88043 1.69000000
88139 1.69000000
88174 1.69000000
88175 1.69000000
88176 1.69000000
88177 1.69000000
88178 1.69000000
88179 1.69000000
88180 1.69000000
88181 1.69000000
88182 1.69000000
88197 1.69000000
88198 1.69000000
88199 1.69000000
88200 1.69000000
88324 1.69000000