$8/kg is a very low price. Ceylon bottoms out around $20/kg in the states. There just isn't the same demand here; tons of ceylon goes to Eurasia, particularly the Middle East, but Americans don't have a history of drinking it. Stuff like sweet tea (popular in the South) is made with Argentinian tea, which is cheaper to import since it doesn't have to cross an ocean. Ahmad, which is probably the most popular mass-market ceylon, goes for $15/kg from a UK distributor but $25/kg from Amazon. I get $20/kg when I shop around for big brands (eg Alwazah, Alghazaleen) at Middle Eastern grocery stores. I do occasionally notice short-lived deals on Ebay or Amazon like this Watawala for $16/kg.

https://www.reddit.com/r/tea/comments/12hhhwq/can_anyone_recommend_a_brand_of_tea_or_a_supplier/

You might consider switching to assam, which hits $10/kg at Indian grocery stores, or generic black tea blends likely from in Africa or Indonesia where labor is cheap.