It's no less moral than selling your labor in other ways, hell, it's less harmful to the self than some other forms of labor.
Capitalism makes all labor morally grey to say the least, most of us work because we have to, engaged in jobs and environments we'd prefer not to be in.
My take is, for labor to be moral(I'm not taliking about personal morality, but systemic) our essentials need to be well covered regardless of our work, and the people need systemic assistance moving from one field to another, so that what ever labor one is engaged in doesn't feel like their only choice of participation.
I don't know where sex work fits into my utopia, but I do know I'd prefer, I'm general, that people are only engaged in what they want to engage in.
Small dick energy