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 (
    60025, 60024, 60023, 60022, 60021, 60020, 
    60019, 60018, 60017, 60016, 60015, 
    60014, 60013, 60012, 60011, 60010, 
    60009, 60008, 60007, 60006
  ) 
  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 0.00078

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
60006 1.69000000
60007 1.69000000
60008 1.69000000
60009 1.69000000
60010 1.69000000
60011 1.69000000
60012 1.69000000
60013 1.69000000
60014 1.69000000
60015 1.69000000
60016 1.69000000
60017 1.69000000
60018 1.69000000
60019 1.69000000
60020 1.69000000
60021 1.69000000
60022 1.69000000
60023 1.69000000
60024 1.69000000
60025 1.69000000