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 (
    11320, 11321, 11322, 11323, 11324, 11325, 
    11326, 11327, 11328, 11329, 11330, 
    11331, 11332, 11333, 11334, 11335, 
    11336, 11337, 11338, 11339, 11340, 
    11341, 11342, 11343, 11344, 11345, 
    11346, 11347, 11348, 11349, 11350, 
    11351, 11352, 11353, 11354, 11355, 
    11356, 11357, 11358, 11359, 11360, 
    11361, 11362, 11363, 11364, 11365, 
    11366, 11367, 11368, 11369, 11370, 
    11371, 11372, 11373, 11374, 11375, 
    11376, 11377, 11378, 11379, 11380, 
    11381, 11382, 11383, 11384, 11385, 
    11386, 11387, 11388, 11389, 11390, 
    11391, 11392, 11393, 11394, 11395, 
    11396, 11397, 11398, 11399, 11400, 
    11401, 11402, 11403, 11404, 11405, 
    11406, 11407, 11408, 11409
  ) 
  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 0.00141

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "88.21"
    },
    "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": 146,
        "rows_produced_per_join": 29,
        "filtered": "20.00",
        "index_condition": "(`gaseus`.`cscart_product_prices`.`product_id` in (11320,11321,11322,11323,11324,11325,11326,11327,11328,11329,11330,11331,11332,11333,11334,11335,11336,11337,11338,11339,11340,11341,11342,11343,11344,11345,11346,11347,11348,11349,11350,11351,11352,11353,11354,11355,11356,11357,11358,11359,11360,11361,11362,11363,11364,11365,11366,11367,11368,11369,11370,11371,11372,11373,11374,11375,11376,11377,11378,11379,11380,11381,11382,11383,11384,11385,11386,11387,11388,11389,11390,11391,11392,11393,11394,11395,11396,11397,11398,11399,11400,11401,11402,11403,11404,11405,11406,11407,11408,11409))",
        "cost_info": {
          "read_cost": "85.29",
          "eval_cost": "2.92",
          "prefix_cost": "88.21",
          "data_read_per_join": "700"
        },
        "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)))"
      }
    }
  }
}