Do Not Pay Any Less, Mrs. Mess Puzzle

Mrs Mess was buying a set of garden furniture.

The bill was seventy dollars.

She gave the attendant what she thought were

two $50 bills, (actually two $100 bills).

The attendant was sleepy and didn't notice either,

so he gave Mrs. Mess what he thought were

three $10 bills (actually three $50 bills).

Who ended up better off than they should?