I think it would be much better if a proper system was implemented:
Have the entire Runescape Market in one giant section, but add some sort of filter as you would in any shopping environment. For example, Someone wants gold, so they check 'gold' and any threads tagged with gold appear. You can further select pricing, etc, and all of this would be controlled through listing different aspects of what you're selling.
Of course, it would requite a lot of work and I don't see this happening.