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 (
    12752, 12753, 12754, 12755, 12756, 12757, 
    12758, 12759, 12760, 12761, 12762, 
    12763, 12764, 12765, 12766, 12767, 
    12768, 12769, 12770, 12771, 12772, 
    12773, 12774, 12775, 12776, 12777, 
    12778, 12779, 12780, 12781
  ) 
  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 0.00119

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "42.01"
    },
    "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": 60,
        "rows_produced_per_join": 60,
        "filtered": "100.00",
        "index_condition": "((`test2_gaseus`.`cscart_product_prices`.`lower_limit` = 1) and (`test2_gaseus`.`cscart_product_prices`.`product_id` in (12752,12753,12754,12755,12756,12757,12758,12759,12760,12761,12762,12763,12764,12765,12766,12767,12768,12769,12770,12771,12772,12773,12774,12775,12776,12777,12778,12779,12780,12781)) and (`test2_gaseus`.`cscart_product_prices`.`usergroup_id` in (0,1)))",
        "cost_info": {
          "read_cost": "36.01",
          "eval_cost": "6.00",
          "prefix_cost": "42.01",
          "data_read_per_join": "1K"
        },
        "used_columns": [
          "product_id",
          "price",
          "percentage_discount",
          "lower_limit",
          "usergroup_id"
        ]
      }
    }
  }
}