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 (
    92901, 92884, 93763, 93762, 93758, 93743, 
    93741, 93740, 93739, 93738, 93737, 
    93736, 93472, 92820, 92345, 89225, 
    93548, 93517, 93345, 92683
  ) 
  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 0.00060

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
89225 1.69000000
92345 1.69000000
92683 1.69000000
92820 1.69000000
92884 1.69000000
92901 1.69000000
93345 1.69000000
93472 1.69000000
93517 1.69000000
93548 1.69000000
93736 1.69000000
93737 1.69000000
93738 1.69000000
93739 1.69000000
93740 1.69000000
93741 1.69000000
93743 1.69000000
93758 1.69000000
93762 1.69000000
93763 1.69000000