Do you even know what you are asking? I suggest you read the whole text of the Divine Liturgy.
What you call sacrifice we call "Gifts." Why do people give gifts, Blogger? Out of love. Out of gratitude. Because God showers us with gifts.
Make sure you notice when, before consecration, the priest says: We offer to You these gifts from Your own gifts in all and for all.
Gifts are "sacrifices" inasmuch as one goes out of his way to acquire them and give them without expecting anything in return. Gifts are labor of love. It's a sactifice alright, a bloodless one. Not something pagans did to buy favors.
What is the Eucharist?