This is a hard one to answer, as it's highly contingent on your industry, price point, and competition. One of our primary producer clients averages a 9% conversion rate, while most of our apparel clients have conversion rates between 2-4%.
Regardless of what rate you're currently seeing, there's always a way to squeeze higher conversions out of your site by running a full CRO audit and committing to an incremental CRO process.