It depends on which kind of solar installation you're talking about. In utility scale projects, modules are still the single largest expense though they're now less than 40% of the total. In residential projects they're also the single largest expense but less than 20% of the total.
See pages 22 and 30 of this 2022 NREL solar cost report:
"U.S. Solar Photovoltaic System and Energy Storage Cost Benchmarks, With Minimum Sustainable Price Analysis: Q1 2022"
The residential market has traditionally been where higher-cost, higher-efficiency panels do best. But efficiency has risen so much across the board in recent years that it appears difficult to run a solar manufacturing business targeting the rooftop market alone. The bigger manufacturers that service all markets have panels that can match or nearly match the efficiency of specialty manufacturers and they have better economies of scale.
See pages 22 and 30 of this 2022 NREL solar cost report:
"U.S. Solar Photovoltaic System and Energy Storage Cost Benchmarks, With Minimum Sustainable Price Analysis: Q1 2022"
https://www.nrel.gov/docs/fy22osti/83586.pdf
The residential market has traditionally been where higher-cost, higher-efficiency panels do best. But efficiency has risen so much across the board in recent years that it appears difficult to run a solar manufacturing business targeting the rooftop market alone. The bigger manufacturers that service all markets have panels that can match or nearly match the efficiency of specialty manufacturers and they have better economies of scale.