I also believe that the larger plots are underpriced, while the silver barrier to plot ownership is too high, unless you are in a guild who has a plot. Make the smaller plots easier to obtain and more affordable, to encourage players to own plots and therefore contribute to this great game financially. The large plots are very much in demand, and in demand means the price can go up, and that there should be more of them.
When I was looking into getting a plot (i was very excited) when I saw one that I liked that was a good size (i think it was a 56x86 or someat) It was WAY out of my price range. I could have gone for a guild plot, but they didn't have the resources nearby and I didn't know about using vault space to getting mats to your buildsite. I wound up having to borrow the 1.2ish gold to buy the land and start building, which was why I subbed in the first place. I would have been very unhappy if it was harder to make friends and I was forced to generate the coin myself to purchase that plot.
Now the really big plots are awesome. I can totally see myself moving into one that was desirably placed, and I don't mind earning it now that I have a little someplace to call home. But I think many of the existing big plots that are currently owned are way undervalued. just my 2 copper...
Sarg