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 (
    120, 121, 122, 123, 124, 125, 126, 127, 
    128, 129, 130, 131, 132, 133, 134, 135, 
    136, 137, 138, 139, 140, 141, 142, 143, 
    144, 145, 146, 147, 148, 149, 150, 151, 
    152, 153, 154, 155, 156, 157, 158, 159, 
    160, 161, 162, 163, 164, 165, 167, 168, 
    169, 170, 171, 172, 173, 174, 175, 176, 
    177, 178, 179, 180, 181, 182, 183, 184
  ) 
  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 0.00099

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "208.45"
    },
    "grouping_operation": {
      "using_temporary_table": true,
      "using_filesort": true,
      "cost_info": {
        "sort_cost": "128.00"
      },
      "table": {
        "table_name": "cscart_product_prices",
        "access_type": "ALL",
        "possible_keys": [
          "usergroup",
          "product_id",
          "lower_limit",
          "usergroup_id"
        ],
        "rows_examined_per_scan": 383,
        "rows_produced_per_join": 128,
        "filtered": "33.42",
        "cost_info": {
          "read_cost": "54.86",
          "eval_cost": "25.60",
          "prefix_cost": "80.46",
          "data_read_per_join": "3K"
        },
        "used_columns": [
          "product_id",
          "price",
          "percentage_discount",
          "lower_limit",
          "usergroup_id"
        ],
        "attached_condition": "((`pankajecarter_systemfour`.`cscart_product_prices`.`lower_limit` = 1) and (`pankajecarter_systemfour`.`cscart_product_prices`.`product_id` in (120,121,122,123,124,125,126,127,128,129,130,131,132,133,134,135,136,137,138,139,140,141,142,143,144,145,146,147,148,149,150,151,152,153,154,155,156,157,158,159,160,161,162,163,164,165,167,168,169,170,171,172,173,174,175,176,177,178,179,180,181,182,183,184)) and (`pankajecarter_systemfour`.`cscart_product_prices`.`usergroup_id` in (0,1)))"
      }
    }
  }
}