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 (
    108997, 97273, 108863, 108847, 108846, 
    110784, 108984, 97010, 97009, 97008, 
    109024, 110785, 108955, 98935, 108976, 
    108865, 108864, 109010, 108876, 108875
  ) 
  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 0.00076

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
97008 1.69000000
97009 1.69000000
97010 1.69000000
97273 1.69000000
98935 1.69000000
108846 1.69000000
108847 1.69000000
108863 1.69000000
108864 1.69000000
108865 1.69000000
108875 1.69000000
108876 1.69000000
108955 1.69000000
108976 1.69000000
108984 1.69000000
108997 1.69000000
109010 1.69000000
109024 1.69000000
110784 1.69000000
110785 1.69000000