Our Gemara on Amud Beis references a monetary custom in silent partner and share cropper agreements. The silent partner can take between ⅔, one half, one quarter for himself. This seemed to be a common financial arrangement that was not considered exploitative, despite the large percentages.

The Midrash (Yalkut Shimoni 892) speaking for God, as if He were justifying the mitzvah to tithe: “It is customary for the owner of the field to rent it out to a sharecropper for only one half, one third or one quarter of its production. But, I (God), only ask for ten percent.”

The Alshich (Devarim 26) expands on this theme in relation to the mitzvah of Bikkurim, offering the first produce to God. He continues the sharecropper parable by saying that it also was customary for the sharecropper to bring the owner of the field its first yields. If the owner was a wealthy man, he could be overcome with gratitude and the good will of this humble farmer’s gift, that he might forgive his percentage. This is the process of the mitzvah of Bikkurim followed by maaser, first is the gift of gratitude, and then this reduces the obligation to only a tenth because God forgives the rest. 

The Gemara Berachos (35a) describes a similar process in regard to all pleasures of this world. 

Rabbi Levi raised a contradiction: It is written: “The earth and all it contains is the Lord’s,” and it is written elsewhere: “The heavens are the Lord’s, while the Earth, He has given over to mankind” (Psalms 115:16). There is clearly a contradiction with regard to whom the Earth belongs. He himself resolves the contradiction: This is not difficult. Here, the verse that says that the earth is the Lord’s refers to the situation before a blessing is recited.

Really everything belongs to God and we should not be permitted to take it, however when we pause to appreciate Him (the Beracha or the Bikkurim), we get to keep the rest.

These devotions and rituals are to teach perspective and gratitude. But whom does this serve? Does God need our sacrifices (Yeshaiyahu 1:11)? Rather the focus on gratitude is to increase our benefit and enjoyment in this world. This is aside from any rewards that await in the World to Come. How do tithing and blessings before eating increase enjoyment? Kuzari (III:16-17) explains it with a parable: A person went to a party and became excessively drunk. The next day, his friends regaled him about all his adventures that night - he had a great time, but sadly, cannot remember a thing. So too, it is easy to rush through life and become intoxicated by all the distractions and pleasures of this world, and in the end, experience nothing. By requiring blessings (and tithing), the Torah reminds you to pause and reflect. The appreciation leads to mindfulness, which leads to a more wholesome and deeper pleasure.