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 (
    82071, 82118, 82073, 82038, 149042, 
    82061, 81948, 82009, 82101, 81647, 
    82133, 82103, 81737, 81655, 82104, 
    81704, 81826, 81863, 81741, 81860, 
    81702, 82072, 81634, 81657, 366904, 
    389637, 81739, 81625, 82115, 81776, 
    82074, 81611, 81862, 81627, 366903, 
    82114, 82069, 81773, 81636, 152085, 
    368409, 366900, 366968, 372041, 391071, 
    81624, 82099, 82052, 82096, 391278, 
    359756, 390761, 424699, 430332, 81747, 
    391070, 82116, 82095, 435209, 435210, 
    430344, 430333, 430573, 430346, 430347, 
    435211, 430329
  ) 
  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 0.00333

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "187.81"
    },
    "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": 134,
        "rows_produced_per_join": 134,
        "filtered": "100.00",
        "cost_info": {
          "read_cost": "161.01",
          "eval_cost": "26.80",
          "prefix_cost": "187.81",
          "data_read_per_join": "8K"
        },
        "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 (82071,82118,82073,82038,149042,82061,81948,82009,82101,81647,82133,82103,81737,81655,82104,81704,81826,81863,81741,81860,81702,82072,81634,81657,366904,389637,81739,81625,82115,81776,82074,81611,81862,81627,366903,82114,82069,81773,81636,152085,368409,366900,366968,372041,391071,81624,82099,82052,82096,391278,359756,390761,424699,430332,81747,391070,82116,82095,435209,435210,430344,430333,430573,430346,430347,435211,430329)) and (`webmarco`.`cscart_product_prices`.`usergroup_id` in (0,1)))"
      }
    }
  }
}