What does Matthew 20:11 mean?

Perspective changes everything. The group of workers hired early in the morning agreed to work a full day in exchange for a denarius each (Matthew 20:1–2). They have done their work. Now they receive their pay right on time, before the sun sets, as the law of Moses required (Deuteronomy 24:14–15). This is the pay they signed on for, given when it was due. Everyone should be satisfied.

Instead, these workers grumble at the master of house. One thing has changed. They have learned what someone else was paid. Those who worked only an hour late in the day have received the same pay as them. Worse, they had briefly expected to be paid more than the original agreement, assuming the master of the house would be generous with them instead of merely honoring their agreement. That failed expectation and change of perspective left them grumbling and complaining despite being treated exactly as they had agreed.