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 (
    138, 139, 140, 141, 142, 143, 144, 145, 
    146, 147, 148, 149, 150, 151, 152, 153, 
    154, 155, 156, 157, 158, 159, 160, 161
  ) 
  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 0.00045

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "102.39"
    },
    "grouping_operation": {
      "using_temporary_table": true,
      "using_filesort": true,
      "cost_info": {
        "sort_cost": "48.00"
      },
      "table": {
        "table_name": "cscart_product_prices",
        "access_type": "ALL",
        "possible_keys": [
          "usergroup",
          "product_id",
          "lower_limit",
          "usergroup_id"
        ],
        "rows_examined_per_scan": 256,
        "rows_produced_per_join": 48,
        "filtered": "18.75",
        "cost_info": {
          "read_cost": "44.79",
          "eval_cost": "9.60",
          "prefix_cost": "54.39",
          "data_read_per_join": "1K"
        },
        "used_columns": [
          "product_id",
          "price",
          "percentage_discount",
          "lower_limit",
          "usergroup_id"
        ],
        "attached_condition": "((`atulecarter_new_april_setup`.`cscart_product_prices`.`lower_limit` = 1) and (`atulecarter_new_april_setup`.`cscart_product_prices`.`product_id` in (138,139,140,141,142,143,144,145,146,147,148,149,150,151,152,153,154,155,156,157,158,159,160,161)) and (`atulecarter_new_april_setup`.`cscart_product_prices`.`usergroup_id` in (0,1)))"
      }
    }
  }
}