Not only these online forms are free, they come with options that other vendors charge you for - unlimited submissions, access to form data by multiple users, field rules (conditional logic), post submit rules, quotes, invoices and online payment options, notifications via email or mobile phone push notifications to name a few.
And because these forms are automatically connected to CRM, you get a lot more information and reporting than a typical online form service provides. You can calculate conversion rates, see how much money each person who filled the form has spent, you can run email and telemarketing campaigns from inside Bitrix24, build sales funnel and pipeline reports.
Bitrix24 CRM manual is available here.
If you are interested in buying self-hosted editions of Bitrix24, which come with API, CMS and source code, can be easily customized and integrated with other tools, please download a trial version here.