Tree Cutting Tree Trimming Services

[Chicago48]

My bro has a backyard tree that needs cutting down. He said he was quoted $5000 to cut the tree. I said, no way. Does it cost $5000 to cut down a tree.

Second question - there's a willow tree hanging next to his property and I tried to look up land rights. I can't find a landowner so I assume it's the city. If it's the city property, shouldn't the city cut it down if it's blocking the sidewalk?
[[Hope you can see the attachment)