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 (
    94011, 94010, 94009, 94008, 94007, 94006, 
    94851, 89228, 94777, 94772, 94133, 
    94760, 92912, 94726, 94708, 94707, 
    94706, 94687, 94570, 94569
  ) 
  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 0.00084

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
89228 1.69000000
92912 1.69000000
94006 1.69000000
94007 1.69000000
94008 1.69000000
94009 1.69000000
94010 1.69000000
94011 1.69000000
94133 1.69000000
94569 1.69000000
94570 1.69000000
94687 1.69000000
94706 1.69000000
94707 1.69000000
94708 1.69000000
94726 1.69000000
94760 1.69000000
94772 1.69000000
94777 1.69000000
94851 1.69000000