SELECT 
  cscart_ult_product_prices.product_id, 
  MIN(
    IF(
      cscart_ult_product_prices.percentage_discount = 0, 
      cscart_ult_product_prices.price, 
      cscart_ult_product_prices.price - (
        cscart_ult_product_prices.price * cscart_ult_product_prices.percentage_discount
      )/ 100
    )
  ) AS price 
FROM 
  cscart_ult_product_prices 
WHERE 
  cscart_ult_product_prices.product_id IN (
    287, 288, 289, 290, 286, 285, 278, 280, 
    282, 247, 248, 241, 244, 245, 246, 240, 
    6, 66, 166, 214, 219, 221, 223, 192, 194, 
    195, 196, 197, 198, 199, 200, 201
  ) 
  AND cscart_ult_product_prices.lower_limit = 1 
  AND cscart_ult_product_prices.company_id = 1 
  AND cscart_ult_product_prices.usergroup_id IN (0, 0, 1) 
GROUP BY 
  cscart_ult_product_prices.product_id

Query time 0.00081

JSON explain

{
  "query_block": {
    "select_id": 1,
    "filesort": {
      "sort_key": "cscart_ult_product_prices.product_id",
      "temporary_table": {
        "nested_loop": [
          {
            "table": {
              "table_name": "cscart_ult_product_prices",
              "access_type": "ALL",
              "possible_keys": [
                "usergroup",
                "product_id",
                "company_id",
                "lower_limit",
                "usergroup_id"
              ],
              "rows": 4,
              "filtered": 100,
              "attached_condition": "cscart_ult_product_prices.lower_limit = 1 and cscart_ult_product_prices.company_id = 1 and cscart_ult_product_prices.product_id in (287,288,289,290,286,285,278,280,282,247,248,241,244,245,246,240,6,66,166,214,219,221,223,192,194,195,196,197,198,199,200,201) and cscart_ult_product_prices.usergroup_id in (0,0,1)"
            }
          }
        ]
      }
    }
  }
}