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 (
    92925, 96737, 97530, 97509, 97439, 97205, 
    97465, 92924, 97437, 97419, 97407, 
    97406, 97403, 97240, 97171, 97033, 
    97024, 96989, 96985, 96594
  ) 
  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 0.00094

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
92924 1.69000000
92925 1.69000000
96594 1.69000000
96737 1.69000000
96985 1.69000000
96989 1.69000000
97024 1.69000000
97033 1.69000000
97171 1.69000000
97205 1.69000000
97240 1.69000000
97403 1.69000000
97406 1.69000000
97407 1.69000000
97419 1.69000000
97437 1.69000000
97439 1.69000000
97465 1.69000000
97509 1.69000000
97530 1.69000000