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 (
    35929, 35931, 35930, 35925, 35923, 32703, 
    32706, 32704, 35917, 35916, 32678, 
    33081, 35928, 35927, 35921, 32679, 
    32687, 32681, 32683, 32696, 32685, 
    32707, 32691, 35912, 32690, 35919, 
    35920, 32695, 32700, 33102
  ) 
  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 0.00184

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "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": 30,
          "filtered": 99.9960556,
          "index_condition": "cscart_product_prices.product_id in (35929,35931,35930,35925,35923,32703,32706,32704,35917,35916,32678,33081,35928,35927,35921,32679,32687,32681,32683,32696,32685,32707,32691,35912,32690,35919,35920,32695,32700,33102)",
          "attached_condition": "cscart_product_prices.lower_limit = 1 and cscart_product_prices.usergroup_id in (0,1)"
        }
      }
    ]
  }
}