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 (
    187, 321, 323, 326, 329, 332, 170, 131, 
    177, 186, 185, 179, 233, 152, 160, 237, 
    235, 122, 115, 129, 127, 188, 336, 124, 
    236, 234, 150, 151, 181
  ) 
  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 0.00066

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "76.61"
    },
    "grouping_operation": {
      "using_filesort": false,
      "table": {
        "table_name": "cscart_product_prices",
        "access_type": "range",
        "possible_keys": [
          "usergroup",
          "product_id",
          "lower_limit",
          "usergroup_id"
        ],
        "key": "product_id",
        "used_key_parts": [
          "product_id"
        ],
        "key_length": "3",
        "rows_examined_per_scan": 34,
        "rows_produced_per_join": 6,
        "filtered": "19.67",
        "index_condition": "(`atulecarter_atul_demo2`.`cscart_product_prices`.`product_id` in (187,321,323,326,329,332,170,131,177,186,185,179,233,152,160,237,235,122,115,129,127,188,336,124,236,234,150,151,181))",
        "cost_info": {
          "read_cost": "75.27",
          "eval_cost": "1.34",
          "prefix_cost": "76.61",
          "data_read_per_join": "160"
        },
        "used_columns": [
          "product_id",
          "price",
          "percentage_discount",
          "lower_limit",
          "usergroup_id"
        ],
        "attached_condition": "((`atulecarter_atul_demo2`.`cscart_product_prices`.`lower_limit` = 1) and (`atulecarter_atul_demo2`.`cscart_product_prices`.`usergroup_id` in (0,1)))"
      }
    }
  }
}