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 (
    9610, 9611, 9612, 9613, 9614, 9615, 9616, 
    9617, 9618, 9619, 9620, 9621, 9622, 
    9623, 9624, 9625, 9626, 9627, 9628, 
    9629, 9630, 9631, 9632, 9633, 9634, 
    9635, 9636, 9637, 9638, 9639, 9640, 
    9641, 10049, 10050, 10051, 10052, 10053, 
    10054, 10055, 10056, 10057, 10058, 
    10059, 10060, 10061, 10062, 10063, 
    10064
  ) 
  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 0.00101

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": "20.00",
        "index_condition": "(`gaseus`.`cscart_product_prices`.`product_id` in (9610,9611,9612,9613,9614,9615,9616,9617,9618,9619,9620,9621,9622,9623,9624,9625,9626,9627,9628,9629,9630,9631,9632,9633,9634,9635,9636,9637,9638,9639,9640,9641,10049,10050,10051,10052,10053,10054,10055,10056,10057,10058,10059,10060,10061,10062,10063,10064))",
        "cost_info": {
          "read_cost": "33.08",
          "eval_cost": "0.98",
          "prefix_cost": "34.06",
          "data_read_per_join": "235"
        },
        "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)))"
      }
    }
  }
}