You can buy cheap mounting equipment on AliExpress. But then you must convince your local building department that your panels won't land on your neighbors in the next storm. That conversation is easier when you're using familiar name-brand mounting equipment that has published and proven all its specs.
Similarly, if you want to do a permitted installation, you generally need to use UL-certified inverters and batteries -- fewer shocks and fires. That's a different pricing tier from the "trust me bro" equipment you can find online.
Meanwhile, a panel's main failure mode is not producing enough power. They're relatively easy to replace when they fail to do that. Price incentives are better aligned for that system component.
Similarly, if you want to do a permitted installation, you generally need to use UL-certified inverters and batteries -- fewer shocks and fires. That's a different pricing tier from the "trust me bro" equipment you can find online.
Meanwhile, a panel's main failure mode is not producing enough power. They're relatively easy to replace when they fail to do that. Price incentives are better aligned for that system component.