Neoclassical Economics: self-interested agents will willingly trade time to businesses for a wage in a labor market, and the magic of competition will ensure efficient (by which we mean best) wage that benefits workers and businesses.
Reality: Fashion models from outside the US often fall into "agency debt" - the costs they pay to the agency for housing, etc. outweighs what they make - to companies who they are often financially and legally required to make money for, making them prime targets of exploitation.
Ayn Rand stans: Hell yes! People should be able to sell themselves into slavery. That's freedom, baby!