not sure...
I am using cosmos, about half of it only and Enhanced Flight Map, Dhask's FlightMap, Gatherer, KCIT, KCET, UBotD, MobInfo2, Titan 2.xx, SmartPet, MyTarget, FlexBar, flagRSP, CTA, CT_RaidAssist and a few others.
Add-ons that use a lot of UI Mem are add-ons that gather a lot of data like LootLink and variations. If you will use one, use KCIT instead as it is more optimized (my KCIT "lootlink" type is only using 1-2mb compared to LootLink's almost 8mb usage).
Then CT_RaidTracker will add about 5-7 mb more so I strongly suggest you don't use it unless necessary.
Overall, I'm only using 40-50mb of UI Mem sometimes it reach up to 53 and that only happens when I've been online for 9 hours straight. Sometimes it also goes down below 50mb even without restarting the game.
To add to that, I have BitComet on in the background with an average of 3 videos downloading.
Oh, profiler add-ons also take UI Mem especially CensusPlus.
Btw, WoWEcon is not accurate
Try to compare the price appearing from WoWEcon to the actual AH price, there's a huge difference. I stopped using it 3 months ago after the error became that huge (and I compared it with 2 highly populated servers).
Additionally, the more addons you have enabled the more it eats up UI Mem. Try to switch to addons that offer the same functionalities as 2 to 5 addons individually are offering.
That will greatly lower your UI Mem and the increments it does.