It should be free. There is absolutely zero reason why I should have to pay to see my credit report at any time, or decide that I wish to freeze my credit at any time.
In another world you wouldn't even be allowed to see your number. It's not like similar agencies -- fraud detection, ad firms, social networks, spam blacklists, etc. -- let you see the profile they've built about you.
They're a for-profit company in the business of selling data, the fact that you're in the market for you own profile, to me, seems immaterial. The only reason you're required to be able to view your report once a year for free is to correct mistakes.
I do not care at all that they're a "for-profit company." I don't believe they should be able to profit on my data without allowing me to see it, and make corrections as needed.