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 (
    269934, 269946, 269972, 269928, 269932, 
    269930, 269960, 269961, 269945, 270059, 
    269950, 269937, 269935, 269933, 269943, 
    269941, 270093, 269981, 269982, 269962, 
    269939, 270136, 270014, 269926, 270012, 
    270097, 269979, 269980, 269824, 269936, 
    270064, 270065, 270022, 269927, 269944, 
    270016, 269963, 270021, 270013, 269942, 
    269966, 270088, 270018, 269925, 269948, 
    269929, 269938, 270137, 270138, 270020, 
    269947, 269958, 269940, 269931, 269959, 
    269978, 269964, 270132, 270133, 269983, 
    270131, 269965, 270023, 270134, 270015, 
    270087, 270017, 270057
  ) 
  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 0.00276

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "190.61"
    },
    "grouping_operation": {
      "using_filesort": false,
      "table": {
        "table_name": "cscart_product_prices",
        "access_type": "range",
        "possible_keys": [
          "usergroup",
          "product_id",
          "lower_limit",
          "usergroup_id"
        ],
        "key": "usergroup",
        "used_key_parts": [
          "product_id",
          "usergroup_id",
          "lower_limit"
        ],
        "key_length": "9",
        "rows_examined_per_scan": 136,
        "rows_produced_per_join": 136,
        "filtered": "100.00",
        "cost_info": {
          "read_cost": "163.42",
          "eval_cost": "27.20",
          "prefix_cost": "190.62",
          "data_read_per_join": "8K"
        },
        "used_columns": [
          "product_id",
          "price",
          "percentage_discount",
          "lower_limit",
          "usergroup_id"
        ],
        "attached_condition": "((`webmarco`.`cscart_product_prices`.`lower_limit` = 1) and (`webmarco`.`cscart_product_prices`.`product_id` in (269934,269946,269972,269928,269932,269930,269960,269961,269945,270059,269950,269937,269935,269933,269943,269941,270093,269981,269982,269962,269939,270136,270014,269926,270012,270097,269979,269980,269824,269936,270064,270065,270022,269927,269944,270016,269963,270021,270013,269942,269966,270088,270018,269925,269948,269929,269938,270137,270138,270020,269947,269958,269940,269931,269959,269978,269964,270132,270133,269983,270131,269965,270023,270134,270015,270087,270017,270057)) and (`webmarco`.`cscart_product_prices`.`usergroup_id` in (0,1)))"
      }
    }
  }
}