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 (
    366926, 366913, 366931, 366914, 366929, 
    366928, 366927, 366936, 366937, 368738, 
    366940, 366915, 368731, 368839, 366930, 
    368772, 366933, 366934, 368698, 368735, 
    366939, 366932, 368733, 366942, 368677, 
    366949, 368770, 368734, 368730, 368716, 
    368829, 368783, 368798, 368740, 366948, 
    368822, 368750, 366947, 366943, 368795, 
    368818, 366938, 368714, 368742, 368715, 
    368797, 366941, 368827, 366950, 368718, 
    368823, 350398, 350316, 355400, 355448, 
    350217, 350261, 350356, 350219, 350578, 
    350251, 355391, 350477, 356841, 350526, 
    350585, 350202, 350542, 350537, 350208, 
    350484, 350212, 353704, 350323, 350539, 
    350211, 350553, 353714, 350510, 350416, 
    350204, 350459, 350213, 350207, 350222, 
    350455, 350225, 350198, 350392, 355393, 
    350505, 350580, 350518, 350528, 355591, 
    353706, 350584, 350320, 350406, 350214
  ) 
  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 0.00176

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "280.31"
    },
    "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": 200,
        "rows_produced_per_join": 200,
        "filtered": "100.00",
        "cost_info": {
          "read_cost": "240.31",
          "eval_cost": "40.00",
          "prefix_cost": "280.31",
          "data_read_per_join": "12K"
        },
        "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 (366926,366913,366931,366914,366929,366928,366927,366936,366937,368738,366940,366915,368731,368839,366930,368772,366933,366934,368698,368735,366939,366932,368733,366942,368677,366949,368770,368734,368730,368716,368829,368783,368798,368740,366948,368822,368750,366947,366943,368795,368818,366938,368714,368742,368715,368797,366941,368827,366950,368718,368823,350398,350316,355400,355448,350217,350261,350356,350219,350578,350251,355391,350477,356841,350526,350585,350202,350542,350537,350208,350484,350212,353704,350323,350539,350211,350553,353714,350510,350416,350204,350459,350213,350207,350222,350455,350225,350198,350392,355393,350505,350580,350518,350528,355591,353706,350584,350320,350406,350214)) and (`webmarco`.`cscart_product_prices`.`usergroup_id` in (0,1)))"
      }
    }
  }
}