SELECT 
  prices.product_id, 
  prices.lower_limit, 
  usergroup_id, 
  prices.percentage_discount, 
  IF(
    prices.percentage_discount = 0, 
    prices.price, 
    prices.price - (
      prices.price * prices.percentage_discount
    )/ 100
  ) as price 
FROM 
  cscart_product_prices prices 
WHERE 
  prices.product_id = 133 
  AND lower_limit > 1 
  AND prices.usergroup_id IN (0, 0, 1) 
ORDER BY 
  lower_limit

Query time 0.00051

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "28.73"
    },
    "ordering_operation": {
      "using_filesort": true,
      "cost_info": {
        "sort_cost": "2.54"
      },
      "table": {
        "table_name": "prices",
        "access_type": "ALL",
        "rows_examined_per_scan": 254,
        "rows_produced_per_join": 2,
        "filtered": "1.00",
        "cost_info": {
          "read_cost": "25.94",
          "eval_cost": "0.25",
          "prefix_cost": "26.19",
          "data_read_per_join": "60"
        },
        "used_columns": [
          "product_id",
          "price",
          "percentage_discount",
          "lower_limit",
          "usergroup_id"
        ],
        "attached_condition": "((`mobikul_delivery_boy_livedemo`.`prices`.`product_id` = 133) and (`mobikul_delivery_boy_livedemo`.`prices`.`lower_limit` > 1) and (`mobikul_delivery_boy_livedemo`.`prices`.`usergroup_id` in (0,0,1)))"
      }
    }
  }
}