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 (
    1199, 1943, 1901, 1200, 1212, 1939, 1211, 
    1568, 1535, 1566, 1567, 1032, 1470, 
    1573, 1917, 1916, 1491, 1496, 1497, 
    1498, 1570, 1571, 1572, 1347
  ) 
  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 0.00115

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_product_prices",
      "access_type": "range",
      "possible_keys": ["usergroup", "product_id", "lower_limit", "usergroup_id"],
      "key": "product_id",
      "key_length": "3",
      "used_key_parts": ["product_id"],
      "rows": 28,
      "filtered": 4.897957802,
      "index_condition": "cscart_product_prices.product_id in (1199,1943,1901,1200,1212,1939,1211,1568,1535,1566,1567,1032,1470,1573,1917,1916,1491,1496,1497,1498,1570,1571,1572,1347)",
      "attached_condition": "cscart_product_prices.lower_limit = 1 and cscart_product_prices.usergroup_id in (0,1)"
    }
  }
}