Why do you thinks people we're willing to pay the bards for there talent in early Greek

I think the reason will be similar with why people want to pay to buy a music from the artists today.

Some people just value the existence of art.

During early greek Era, probably there were not many people who can play music since there were no learning material as its today. So the bards from that era probably blessed with raw musical talent

The most likely reason was the associated prestige with having a bard play at your feast for example. This showed the people you had money, but it also served as a nice addition to the event where you were as such people always increased the added value of where they appeared.