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 (
    110297, 110296, 110295, 110294, 110293, 
    110292, 110291, 109632, 109631, 109630, 
    109629, 109627, 110150, 110091, 109592, 
    110153, 110152, 110151, 109581, 110038
  ) 
  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 0.00106

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
109581 1.69000000
109592 1.69000000
109627 1.69000000
109629 1.69000000
109630 1.69000000
109631 1.69000000
109632 1.69000000
110038 1.69000000
110091 1.69000000
110150 1.69000000
110151 1.69000000
110152 1.69000000
110153 1.69000000
110291 1.69000000
110292 1.69000000
110293 1.69000000
110294 1.69000000
110295 1.69000000
110296 1.69000000
110297 1.69000000