Samsung is offering trade-in value on your current devices until the end of June. You can save upto AED 1,860 off the new S9 phones which is almost 50% of the cost of the phones.
Samsung has published a list on how much it thinks your Samsung, Apple or Huawei phones are worth and that list can be accessed here. To give you some examples, The Galaxy Note 8 will get you AED 1,860 while the Galaxy S8+ will get you AED 1,687.
You can get your device valued at one of the Samsung Experience Stores if it's not on that list. The trade-in is also available through other retailers such as Jumbo, Harman House and Sharaf DG.