When you study regional integration in the EAC, you'll realise that this issue goes all the way even to Tariff barriers.
Kenya has currently waived all tariffs on Ugandan and Tanzanian products brought to Kenya. This means that products imported from these countries pay no 'tax' otherwise reffered to as 'tariffs'.
On the other hand, Uganda and TZ charge a 5% Tariff on kenyan products that are exported to their markets. The reason Kenya allows this to happen is mainly based on some sort of 'good faith' because TZ and UG governments claim that they really need that 5% tariff to supplement their Govt income, which are considerably lower than that of the Kenyan Govt.
This 5% tariff however also means that TZ and UG end up shooting themselves in the foot, because the goods will have to be sold at a higher cost, to meet the tax charged. In simpler terms, The two Governments end up earning a lot of money, but the citizens suffer because products become very expensive to buy.
(Keep the coments on facts. No insults or petty talk)