If TurboTax detected your tax situation required expanded coverage, like deductions for owning a home or self-employment income, you may have been prompted to upgrade to a version that supports the forms you need. You then would be charged that amount for an upgrade.
Please see the following FAQ for more details.
Why do I have to upgrade from Free Edition?
You can also downgrade to a lower-priced version, but it would require you to start over.
Can I downgrade to a lower-priced version of TurboTax Online?