This includes solo freelancers though? So I've always seen the advice that to earn more, you can't be seen as a replaceable commodity and you need to attract cl

This includes solo freelancers though? So I've always seen the advice that to earn more, you can't be seen as a replaceable commodity and you need to attract clients that want to work with you in particular. This ruins that? I heard that as long as your contract includes something about how you could be replaced by someone equally skilled, you can work around this? The client can still terminate the contract if they didn't like the replacement.