Starting at $120 USD per company per month Please see Breadwinner's website for pricing information. https://breadwinner.com/quickbooks-online-salesforce/pricing/
Breadwinner for QuickBooks Online offers a powerful two-way integration solution that easily connects QuickBooks Online and Salesforce. Gain access to imperative data in real-time by using Breadwinner’s intuitive and flexible integration.
Full Terms and Conditions are listed at https://breadwinner.com/master-subscription-agreement/