First, the Roman Catholics don't believe in the 10% tithe. The bible doesn't require it. It's mostly the function of greedy churches that pervert rare pieces of scripture as a mandatory donation to the church itself.
What other "churches" do seems rather irrelevant to this topic. The issue was the Catholic church and the Catholics don't set the recommendation at 10%, only 2.5%.
It's not me. If you want to discuss scripture with me, we can do so in another forum or in private message, but I'll stand by my statements based on scripture or anything else. The word of the almighty one is perverted by most of organized churches.
I did not specify Catholic or any other churches, only the historical and literal translation and meaning of the tithe. If Catholics choose to calculate it another way, they certainly can.
And if you do a search of a number of Catholic organization web sites you will find a vast amount of support for the 10% interpretation. You will also find justifications not to expect, demand, or require the tithe but to give only that which you desire.
So, you can argue that it was the function of "greed" if you wish, and you can even pretend that it is not there or justify a lower number, but it is well established what the tithe represents. I really have no care to debate the issue as it seems you have your mind, so it would be a waste of time to engage in such a theological and historical discussion.
So, if the Catholic Church officially asks for 2.5% for giving, that's fine. They are free to do as they wish, and I am sure there is some reasonable calculations that went into this (assuming it is church-wide - and I cannot find support for that). But, that is not the number supported by Biblical reference.