Hi Sara,
There are some missing factors, such as what your current Magento version is, and how many extensions you're using. Factors like these can impact the labor to upgrade your site.
However, keep in mind that 2 weeks is not typically for straight, continuous development time. First the developers need to wrap up whatever else they're working on. Then they'll typically upgrade your site in a local or development environment. They'll update extensions as well. Then there's a testing phase, and potentially work to address code conflicts and errors that may (or may not) pop up. Then, they'll roll the changes out to a staging copy of your site, which mimics the real live hosting environment of your site for further testing. Often, you'll be asked to test the site, and further adjustment could be needed, before they ultimately schedule to push the updates out to your live "production" copy of the site.
While they're waiting for your feedback and approval, they'll typically switch to working on something else (rather than just sit waiting), and they'll often finish whatever that task was before coming back to address your feedback from testing. Sort of like a doctor that goes to check on another patient while waiting a nurse to administer tests on you.
Different developers can have different flows, but long story short, 2 weeks is not an unreasonable expectation to be set for a thorough, well-executed process. From my perspective, it could certainly wrap up faster depending on a variety of factors, but service industry professionals rarely quote the minimum time. If they do, it's all that people hear, and it doesn't do a good job of managing expectations, which simply leads to unhappy business relationships.
I hope this feedback is helpful, and that your Magento upgrade goes quickly and smoothly!
