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 (
    10768, 10767, 10766, 10765, 10764, 10763, 
    10762, 10761, 10760, 10759, 10758, 
    10757, 10756, 10755, 10754, 10753, 
    10752, 10751, 10750, 10749, 10748, 
    10747, 15736, 15737, 15738, 15739, 
    15740, 15741, 15742, 15743, 15745, 
    15746
  ) 
  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 0.00076

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 (10768,10767,10766,10765,10764,10763,10762,10761,10760,10759,10758,10757,10756,10755,10754,10753,10752,10751,10750,10749,10748,10747,15736,15737,15738,15739,15740,15741,15742,15743,15745,15746)",
      "attached_condition": "cscart_product_prices.lower_limit = 1 and cscart_product_prices.usergroup_id in (0,1)"
    }
  }
}

Result

product_id price
10747 6184.31000000
10748 6184.31000000
10749 6184.31000000
10750 6184.31000000
10751 6184.31000000
10752 6184.31000000
10753 7644.03000000
10754 7644.03000000
10755 7644.03000000
10756 7644.03000000
10757 7644.03000000
10758 7644.03000000
10759 3264.87000000
10760 3264.87000000
10761 3264.87000000
10762 3264.87000000
10763 3264.87000000
10764 3264.87000000
10765 3264.87000000
10766 3264.87000000
10767 5972.60000000
10768 5972.60000000
15736 3955.73000000
15737 3955.73000000
15738 3955.73000000
15739 3955.73000000
15740 3955.73000000
15741 3955.73000000
15742 3955.73000000
15743 3955.73000000
15745 3955.73000000
15746 3955.73000000