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 (
    4678, 4817, 4839, 4674, 4519, 4823, 4693, 
    4673, 4816, 4516, 4695, 4822, 4334, 
    4681, 4675, 4688, 4696, 4827, 4820, 
    4830, 4679, 4814, 4819, 4322, 4834, 
    4694, 4682, 4690, 4261, 4686, 4672, 
    4510, 4815, 4689, 4687, 4826, 4677, 
    4829, 4050, 4691, 4697, 4692, 4523, 
    4676, 4658
  ) 
  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 0.00175

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "31.51"
    },
    "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": 45,
        "rows_produced_per_join": 8,
        "filtered": "19.99",
        "index_condition": "(`softwarepirmam_hewadelivard_cscart_4`.`cscart_product_prices`.`product_id` in (4678,4817,4839,4674,4519,4823,4693,4673,4816,4516,4695,4822,4334,4681,4675,4688,4696,4827,4820,4830,4679,4814,4819,4322,4834,4694,4682,4690,4261,4686,4672,4510,4815,4689,4687,4826,4677,4829,4050,4691,4697,4692,4523,4676,4658))",
        "cost_info": {
          "read_cost": "30.61",
          "eval_cost": "0.90",
          "prefix_cost": "31.51",
          "data_read_per_join": "215"
        },
        "used_columns": [
          "product_id",
          "price",
          "percentage_discount",
          "lower_limit",
          "usergroup_id"
        ],
        "attached_condition": "((`softwarepirmam_hewadelivard_cscart_4`.`cscart_product_prices`.`lower_limit` = 1) and (`softwarepirmam_hewadelivard_cscart_4`.`cscart_product_prices`.`usergroup_id` in (0,1)))"
      }
    }
  }
}