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 (
    951, 950, 949, 948, 947, 946, 945, 944, 
    943, 942, 941, 940, 939, 938, 937, 936, 
    935, 932, 931, 930, 929, 928, 927, 919, 
    918, 917, 517, 516, 515, 478, 477, 476, 
    475, 474, 464, 460, 434, 433, 432, 431, 
    428, 427, 424, 423, 422, 421, 420, 419
  ) 
  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 0.00070

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "34.06"
    },
    "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": 49,
        "rows_produced_per_join": 9,
        "filtered": "19.95",
        "index_condition": "(`wearethehelpful_scalesta_net`.`cscart_product_prices`.`product_id` in (951,950,949,948,947,946,945,944,943,942,941,940,939,938,937,936,935,932,931,930,929,928,927,919,918,917,517,516,515,478,477,476,475,474,464,460,434,433,432,431,428,427,424,423,422,421,420,419))",
        "cost_info": {
          "read_cost": "33.08",
          "eval_cost": "0.98",
          "prefix_cost": "34.06",
          "data_read_per_join": "234"
        },
        "used_columns": [
          "product_id",
          "price",
          "percentage_discount",
          "lower_limit",
          "usergroup_id"
        ],
        "attached_condition": "((`wearethehelpful_scalesta_net`.`cscart_product_prices`.`lower_limit` = 1) and (`wearethehelpful_scalesta_net`.`cscart_product_prices`.`usergroup_id` in (0,1)))"
      }
    }
  }
}