This has been my experience ~80% of the time. In the remaining ~20%, prices vary by channel. A good example of this is HU between SHA and PEK. HU's flights tend to be the least popular due to a variety of reasons, but their fares often match the rest of the field. However, if you walk into one of their ticket offices, you might find yourself pleasently surprised. Also, in the past, local agents have had access to more inventory than agents in other cities; this is less often the case these days.