You're probably familiar with the term "barter"—in the sense of exchanging goods or services for other goods or services, instead of for money. But the word can also mean the negotiation, or argument, over the terms of a transaction. That's what's really going on in this poem. The speaker is presenting us, the reader, with the terms under which life will provide us with loveliness.
In the poem, the speaker is bartering with the reader. She is arguing that we must accept life's terms—that we will get to experience the loveliness life has to offer if we also accept all of life's hardship and strife.
The title basically sets the reader up for a big game of Let's Make a Deal. The speaker thinks we should accept whatever life offers, even if it isn't the all-expenses-paid trip to Hawaii. We might still get a nice boom-box (Google it) and some sweet tunes to enjoy if we just agree to play the game.