The Talmud (Megillah 12a) gives two different opinions on the matter of couches. The first opinion, that of R’ Yehudah states that there were golden couches for those who deserved them, and silver couches for people of lesser status who did not deserve gold couches. R’ Nechemiah disagrees that this could have been the case, and insists that the couches were all equally made of gold and silver. After all, this would otherwise cause jealousy among the party participants. In Mayan Beis HaSho’eivah (pg. 446-7), Rav Shimon Schwab (zt”l) asks why R’ Nechemiah would think that Achashverosh would put forethought into avoiding jealousy. He answers that the entire design of the party was to make everybody happy, and a person cannot be happy when jealous.