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 (
    415240, 185498, 206442, 209099, 149369, 
    415293, 282473, 149445, 149436, 220056, 
    149383, 149377, 220029, 149449, 185470, 
    149398, 149453, 149399, 220054, 220033, 
    381767, 149373, 220036, 270167, 275684, 
    270168, 262997, 263001, 185469, 185502, 
    270264, 263000, 270378, 185490, 270170, 
    185487, 185495, 185501, 270196, 270202, 
    270231, 185473, 263002, 270377, 185464, 
    270193, 275686, 270272, 270369, 276860, 
    262999, 270169, 270226, 185472, 270370, 
    270371, 270195, 275683, 270194, 270205, 
    270171, 185463, 185475, 185491, 185488, 
    185493, 276862, 276870, 185465, 185466, 
    270227, 276871, 270204, 270373, 185468, 
    185471, 270206, 270273, 309380, 270268, 
    270225, 185499, 309377, 185474, 309382, 
    309381, 309378, 270199, 275685, 270230, 
    309379, 185467, 270229, 185482, 270379, 
    270380, 270270, 185483, 185481, 185503
  ) 
  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 0.00168

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 (415240,185498,206442,209099,149369,415293,282473,149445,149436,220056,149383,149377,220029,149449,185470,149398,149453,149399,220054,220033,381767,149373,220036,270167,275684,270168,262997,263001,185469,185502,270264,263000,270378,185490,270170,185487,185495,185501,270196,270202,270231,185473,263002,270377,185464,270193,275686,270272,270369,276860,262999,270169,270226,185472,270370,270371,270195,275683,270194,270205,270171,185463,185475,185491,185488,185493,276862,276870,185465,185466,270227,276871,270204,270373,185468,185471,270206,270273,309380,270268,270225,185499,309377,185474,309382,309381,309378,270199,275685,270230,309379,185467,270229,185482,270379,270380,270270,185483,185481,185503)) and (`webmarco`.`cscart_product_prices`.`usergroup_id` in (0,1)))"
      }
    }
  }
}