A high-efficiency central AC is a major home system; even "small" repairs can involve diagnostics, labor, and proprietary electronics. Common repair items include the control board, contactors/capacitors, sensors, and blower-related components, plus refrigerant leaks in some cases.
Repair is usually worthwhile when the system is well under mid-life and the issue is a single electronic component (like a control board) that stays under the threshold-because a full replacement is a large installed expense and may require refrigerant line and thermostat considerations. Replacement becomes more attractive when there are repeated refrigerant issues, compressor problems, or multiple costly failures in a short span, since reliability and comfort risk increase.
Age is crucial: if the unit is near or beyond typical service life, putting a large board repair into an aging compressor system can be poor value. Also weigh warranty status and the availability of OEM boards.