Certainly, if I wanted to get a 24" iMac, my work budget pretty much covers it. I can get up to 4GB of RAM and a 2.8 or 3.0GHz Core 2 Duo, which is plenty for my immediate needs, modulo the annoyance that I can't just swap out the computer and keep the monitor.
24in Imac plus existing 23in monitor equals more pixels altogether than a 30in monitor... depends how bad the much wider, shorter form factor would be for the use you make of it.
With discount, I can get a stripped Mac Pro tower (2GB of RAM, minimum disk, 2.8 GHz Core Xeon (quad), etc.) for $2149. For contrast, Dell will sell me a loaded "Studio XPS" (Core i7 (2.9GHz, also quad), 12GB of RAM, 750GB disk, and a beefier graphics card) for essentially the same price ($2139). If I strip the Dell down to be more comparable to the stripped Mac Pro tower, it costs $1119 -- half the price, faster CPU, and still with more memory and disk! I'd always thought that, with the Intel transition, Apple's prices were no longer insane. That's clearly not true here and it's quite frustrating.
I think what happened there, is that Apple priced the Mac Pros when the Core 2 Quad Xeons came out, and hasn't reduced the prices since. Those chips are now a whole generation out of date, the chip price has gone way down, and Dell has followed it but Apple haven't.
Having said all that, my trusty old first-generation Mac Pro with its 30in monitor remains the nicest PC I've ever owned, and I've not regretted the expenditure for a minute.
Peter