In all parts of the world I'm familiar with, that's impossible.
$10 is often the min. price for prepaid service alone. If you consider the US, for example, you could walk away with a phone that is gratis only if you sign a contract that commits you to spending more than the retail cost of the phone over the course of the contract. So it's a steep price and you're also not going to be able to do that without giving up your identity.
At best, one can buy a used phone (without calling credit) for the equivalent of $5 usd. That is still tricky to do anonymously when second-hand markets often block Tor, verify email, and the like. If you manage to get a phone anonymously, the next problem is that all accounts for postpaid service require identity disclosure, and many countries also impose identity-compromising registration for prepaid service. If you avoid that problem by traveling to a country that does not require registration, the next problem is gsm/cdma tracking, which can easily compromise your identity if you're not tinfoil-hat-diligent.
So Steemit accounts are not gratis. The price is your freedom or your money, or (in most cases) you'll give up both.
RE: You must have mistaken STEEM for something else...