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 (
    10708, 10709, 10710, 10711, 10712, 10301, 
    10302, 10303, 10304, 9945, 10601, 9727, 
    9728, 9729, 9730, 9731, 9732, 9733, 
    10181, 9734, 9735, 9724, 10370, 10372, 
    10374, 10376, 10377, 10378, 10379, 
    10380, 10381, 10371
  ) 
  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 0.00067

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 (10708,10709,10710,10711,10712,10301,10302,10303,10304,9945,10601,9727,9728,9729,9730,9731,9732,9733,10181,9734,9735,9724,10370,10372,10374,10376,10377,10378,10379,10380,10381,10371)",
      "attached_condition": "cscart_product_prices.lower_limit = 1 and cscart_product_prices.usergroup_id in (0,1)"
    }
  }
}

Result

product_id price
9724 1482.01000000
9727 1482.01000000
9728 1482.01000000
9729 1482.01000000
9730 1482.01000000
9731 1482.01000000
9732 1482.01000000
9733 1482.01000000
9734 1482.01000000
9735 1482.01000000
9945 1482.01000000
10181 1482.01000000
10301 4579.74000000
10302 4579.74000000
10303 4579.74000000
10304 4579.74000000
10370 2763.44000000
10371 2763.44000000
10372 2763.44000000
10374 2763.44000000
10376 2763.44000000
10377 2763.44000000
10378 2763.44000000
10379 2763.44000000
10380 2763.44000000
10381 2763.44000000
10601 1482.01000000
10708 3432.02000000
10709 3432.02000000
10710 3432.02000000
10711 3432.02000000
10712 3432.02000000