TBOM - surely the law is the same for men and women? Both sexes are allowed to participate in clinical trials, but neither sex are allowed to sell their organs. So I'm not sure how you are arguing that there is a difference in terms of men being able to use their bodies as commodities more frequently, when this is clearly not the case in our society.
Clinical trials are of much more importance to society as a whole than surrogacy is, and there are a variety of laws in place determining the limits on what people can do for money with their own bodies within a work context, including in clinical trials.
As for the idea that women should be able to commodify or exploit men's bodies in the way that men currently commodify or exploit women's - I have no idea what that has to do with this thread, but I certainly don't think feminists should be encouraging the commodification of any human being.
People living in poverty have always done physically problematic things to themselves in order to work. Look at matchbox girls - should we have let them take up employment that ended up losing parts of their faces, or should we have put in employment laws to end that way of working - despite these women 'knowing their own minds.'
To argue for surrogacy as a paid job is to ignore the current exploitation of women's bodies and the climate towards women that we are currently living in.
Quite apart from that, the idea that women should be paid to have other people's children but not their own again supports the idea that being a mother to your own children does not constitute work that society should be paying for. If we paid poor women properly to be mothers, they wouldn't need to have other people's for profit.