Not sure about pricing in your area, so its hard to suggest, I have only looked at higher end since I'm looking to replace adequate units already. Sorry. Like Cleeve says $75 is a good price, and replacement bulbs are much cheaper now (relatively speaking).
Being owners, what are some of the other considerations I should be looking out for? Obviously a plasma will be a better quality image. How big is the difference with a projector. Its always so hard to get info and make a decision, unless you have the thing setup in your room and call pull the trigger.
Well the main issues is the type of environment you'll be projecting into, darkened rooms are great for projectors (and bad for LCD panels, and even Plasmas to a lesser extent). However a bright room usually results in slight wash out. And if you have changing conditions you will want to ensure you have some preset settings you can easily flip between. You can minimize that with specialized screens, and there's even a special reflective paint. But many people use white walls or DIY screens can achieve good results too, but are more prone to outside influences.
As my experience at home is limited to my decade old behemoth (about 3ft long) and then the basics for ours at work, I'm probably not the best person to ask about mixed and HD content as I use DVD or SDTV content at home (for specific activities) and just M$ Office docs at work (we use the Plasma for gaming caue it's infront of the big couch 8) ). Like Paul or Cleeve can give you some insight into the mixed media handling of their model.
Also lamp life is dependant on brightness (as well as contast in that it's a function of brightness), usually lamp hours are about 2/3 to 1/2 or less than listed because that's under ideal conditions with low brightness and not contrast+ features enabled. Also adequate cooling affects them, especially towards end of life.
DLP projectors have better (less noticeable but still sharp) pixel borders than LCD, so I've found them to be great for text and video, without noticeable grid patterns, etc; and if you don't experience the rainbow effect, it's an awesome display best in class IMO, the 3 DLP models beat Plasma IMO. The only weak spot like I mentioned is bright environments.