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, 82101, 82009, 81647, 
    82133, 82103, 81737, 81655, 82104, 
    81704, 81826, 81863, 81741, 81860, 
    81702, 82072, 81634, 81657, 81739, 
    81625, 82115, 81776, 82074, 81862, 
    81627, 82114, 82069, 81773, 81636, 
    81624, 82099, 82052, 82096, 81747, 
    82116, 82095
  ) 
  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 0.00227

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "117.74"
    },
    "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": 84,
        "rows_produced_per_join": 84,
        "filtered": "100.00",
        "cost_info": {
          "read_cost": "100.94",
          "eval_cost": "16.80",
          "prefix_cost": "117.74",
          "data_read_per_join": "5K"
        },
        "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 (82071,82118,82073,82038,149042,82061,81948,82101,82009,81647,82133,82103,81737,81655,82104,81704,81826,81863,81741,81860,81702,82072,81634,81657,81739,81625,82115,81776,82074,81862,81627,82114,82069,81773,81636,81624,82099,82052,82096,81747,82116,82095)) and (`webmarco`.`cscart_product_prices`.`usergroup_id` in (0,1)))"
      }
    }
  }
}