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 (
    451454, 436557, 436005, 422676, 427654, 
    406498, 438920, 440047, 403424, 402161, 
    426357, 413770, 421856, 453293, 421836, 
    444708, 429476, 413127, 407471, 409966, 
    403355, 408795, 420652, 443583
  ) 
  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 0.00230

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost": 0.099614043,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_product_prices",
          "access_type": "range",
          "possible_keys": [
            "usergroup",
            "product_id",
            "lower_limit",
            "usergroup_id"
          ],
          "key": "usergroup",
          "key_length": "9",
          "used_key_parts": ["product_id", "usergroup_id", "lower_limit"],
          "loops": 1,
          "rows": 48,
          "cost": 0.08425304,
          "filtered": 50,
          "attached_condition": "cscart_product_prices.lower_limit = 1 and cscart_product_prices.product_id in (451454,436557,436005,422676,427654,406498,438920,440047,403424,402161,426357,413770,421856,453293,421836,444708,429476,413127,407471,409966,403355,408795,420652,443583) and cscart_product_prices.usergroup_id in (0,1)"
        }
      }
    ]
  }
}