Is it permissible to sell men's perfumes that were bought for 400 Riyals and sell them for 1100 Riyals online, and is that considered deceiving people, knowing that there is no specific profit margin in Islamic law?

As long as the sale is by mutual consent and involves no deception or fraud, it is permissible. A mere increase in profit is not deception and there is no harm in it, because the Sharia (definition) has not set a limit for profit. Urwah sold two sheep to the Prophet, peace be upon him, for a dinar, and then sold one of them for a dinar, profiting from it. Similarly, Al-Zubayr bought Al-Ghabah for one hundred and seventy thousand [dirhams], and his son Abdullah sold it for one million six hundred thousand. However, it is recommended for a Muslim to be lenient and gentle in their buying and selling.