Cost of academic regalia ÷ number of wearings thus far = $160.00 per use.
As a return on value, that's not so bad--in just two or three more years the cost will be the same as if I'd shelled out for rentals each time.
By contrast, consider this equation:
[(money earned over three years of full-time employment + money earned over six years in graduate school) - (educational debt + consumer debt related to the profession)] ÷ nine years = an average annual salary too grim for me to contemplate.
Conclusion: as extravagances go, pretty clothes ain't got nothing on graduate school.