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 (
    96060, 95699, 95231, 93055, 89231, 96061, 
    95337, 92918, 96004, 96003, 96002, 
    95999, 95972, 95837, 95802, 95740, 
    95700, 95697, 95062, 95040
  ) 
  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 0.00112

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
89231 1.69000000
92918 1.69000000
93055 1.69000000
95040 1.69000000
95062 1.69000000
95231 1.69000000
95337 1.69000000
95697 1.69000000
95699 1.69000000
95700 1.69000000
95740 1.69000000
95802 1.69000000
95837 1.69000000
95972 1.69000000
95999 1.69000000
96002 1.69000000
96003 1.69000000
96004 1.69000000
96060 1.69000000
96061 1.69000000