That works both ways, it's not them paying you a salary, it's an exchange of salary for your time and skills.
A willingness to give away your time for free is an indication you don't value yourself that highly.
A willingness to give away your time for free is an indication you don't value yourself that highly.
Nobody is asking for free work. And I definitely would never hire someone that calls a four hour exercise that is part of an application process "an indication you don't value yourself highly." In fact, it would be a huge red flag and I'd throw that applicant'a resume into the trash can.
If you can't see the symmetry in the situation it says something about your values, but it is not a compelling argument.