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 (
    94857, 94814, 95739, 95696, 95695, 89230, 
    95546, 95200, 94865, 94683, 93093, 
    92916, 95501, 95500, 95499, 95498, 
    95497, 95496, 95495, 95494
  ) 
  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 0.00102

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
89230 1.69000000
92916 1.69000000
93093 1.69000000
94683 1.69000000
94814 1.69000000
94857 1.69000000
94865 1.69000000
95200 1.69000000
95494 1.69000000
95495 1.69000000
95496 1.69000000
95497 1.69000000
95498 1.69000000
95499 1.69000000
95500 1.69000000
95501 1.69000000
95546 1.69000000
95695 1.69000000
95696 1.69000000
95739 1.69000000