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 (
    10759, 10760, 10761, 10762, 10763, 10764, 
    10765, 10766, 9874, 9875, 9887, 9879, 
    9796, 9942, 9943, 9941, 9944, 10813, 
    10814, 10815, 10816, 10817, 10818, 
    10819, 10820, 10821, 10822, 10823, 
    10824, 10825, 10826, 12969
  ) 
  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 0.00408

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_product_prices",
      "access_type": "range",
      "possible_keys": ["usergroup", "product_id", "lower_limit", "usergroup_id"],
      "key": "product_id",
      "key_length": "3",
      "used_key_parts": ["product_id"],
      "rows": 32,
      "filtered": 99.23484039,
      "index_condition": "cscart_product_prices.product_id in (10759,10760,10761,10762,10763,10764,10765,10766,9874,9875,9887,9879,9796,9942,9943,9941,9944,10813,10814,10815,10816,10817,10818,10819,10820,10821,10822,10823,10824,10825,10826,12969)",
      "attached_condition": "cscart_product_prices.lower_limit = 1 and cscart_product_prices.usergroup_id in (0,1)"
    }
  }
}

Result

product_id price
9796 1704.87000000
9874 1704.87000000
9875 1704.87000000
9879 1704.87000000
9887 1704.87000000
9941 1704.87000000
9942 1704.87000000
9943 1704.87000000
9944 1704.87000000
10759 3264.87000000
10760 3264.87000000
10761 3264.87000000
10762 3264.87000000
10763 3264.87000000
10764 3264.87000000
10765 3264.87000000
10766 3264.87000000
10813 1704.87000000
10814 1704.87000000
10815 1704.87000000
10816 1704.87000000
10817 1704.87000000
10818 1704.87000000
10819 1704.87000000
10820 1704.87000000
10821 1704.87000000
10822 1704.87000000
10823 1704.87000000
10824 1704.87000000
10825 1704.87000000
10826 1704.87000000
12969 1606.00000000