I've seen the Viewsonic VP912B drop from $609 to $599 to $589 to $559 in the space of about a week at Newegg.com just this past week! Other "cheap" 19" monitors are barely over $300 at this point... but personally I wouldn't want a $300 buck 19" monitor, as most of them have "quaility issues" (like poor response times and no DVI inputs).
I spend more time looking/using the monitor then any other part of my computer, so I have no problems if it's the most expensive piece in my setup (and it's usually the longest-life item to not get replaced). I wouldn't budget a monitor to the lowest cost, but to answer the original question, I'd say you'll see your first CHEAP-O 19" LCD monitor by April 05 (if not sooner).