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 (
    2341, 2342, 2343, 2344, 2345, 2346, 2347, 
    2348, 2421, 2422, 2423, 2424, 2425, 
    2426, 2427, 2428, 2429, 2430, 2431, 
    2432, 2433, 2434, 2435, 2436, 2437, 
    2438, 2519, 2520, 2521, 2522, 2523, 
    2524, 2525, 2526, 2527, 2608, 2609, 
    2610, 2611, 2612, 2613, 2614, 2615, 
    2616, 5872, 5873, 5874, 5875, 5940, 
    5941, 5942, 5943, 5944, 5945, 5946, 
    5947, 5948, 6021, 6022, 6023, 6024, 
    6025, 6026, 6027, 6028, 6029, 6030, 
    6031, 6032, 6033, 6034, 6035, 6036, 
    6037, 6038, 6111, 6112, 6113, 6114, 
    6115, 6116, 6117, 6118, 6119, 6201, 
    6202, 6203, 6204, 6205, 6206, 6207, 
    6208, 3033, 3034, 3035, 3036
  ) 
  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 0.00221

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "67.21"
    },
    "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": 96,
        "rows_produced_per_join": 19,
        "filtered": "20.00",
        "index_condition": "(`gaseus`.`cscart_product_prices`.`product_id` in (2341,2342,2343,2344,2345,2346,2347,2348,2421,2422,2423,2424,2425,2426,2427,2428,2429,2430,2431,2432,2433,2434,2435,2436,2437,2438,2519,2520,2521,2522,2523,2524,2525,2526,2527,2608,2609,2610,2611,2612,2613,2614,2615,2616,5872,5873,5874,5875,5940,5941,5942,5943,5944,5945,5946,5947,5948,6021,6022,6023,6024,6025,6026,6027,6028,6029,6030,6031,6032,6033,6034,6035,6036,6037,6038,6111,6112,6113,6114,6115,6116,6117,6118,6119,6201,6202,6203,6204,6205,6206,6207,6208,3033,3034,3035,3036))",
        "cost_info": {
          "read_cost": "65.29",
          "eval_cost": "1.92",
          "prefix_cost": "67.21",
          "data_read_per_join": "460"
        },
        "used_columns": [
          "product_id",
          "price",
          "percentage_discount",
          "lower_limit",
          "usergroup_id"
        ],
        "attached_condition": "((`gaseus`.`cscart_product_prices`.`lower_limit` = 1) and (`gaseus`.`cscart_product_prices`.`usergroup_id` in (0,1)))"
      }
    }
  }
}