Two reasons, potentially: 1. Principles. 2. If you find another site that gives immediate pricing, you can use it for any subsequent purchases in a similar domain, or they may also be more respectful of your time in other respects (e.g. support), saving time in the long run.

Besides, it stands to reason that googling around for a few more minutes is less time and hassle than waiting for one or more e-mail round trips with humans in the loop for the quote process.