You can buy a really really good high quality vintage steel lugged bike with high quality parts that will last forever - like Campy NR or SR - and find them routinely for $300-$400. They will be used and perhaps a little dirty and may need new tires, new cables, new brake pads and such but they will be great rides. They will last virtually forever if taken care of and will actually go up in price. I fully expect to have my 1973 Raleigh International, my 198? Benotto 850, my 1981 Bianchi (all NR - not junk), and my newly purchased Casati 1983 NOS all Campy Victory for the rest of my life.
But - my everyday bike that I take to out-of-town rides and such is a 2005 Lemond Tourmalet Triple with new DA and Ultegra upgraded components. I expect the frame to last many years, but not as long as my steel classics. I bought the Lemond for ease of riding (triple crank/STI shifters) because I am older now and prefer to sit down while climbing hills - I ain't into being the first up the hill anymore - but my steel classics will probably be around long after the Lemond aluminum frame is worn out (although Lemond does warrant their frames for life).
I don't think you can go wrong investing in a classic steel lugged bike with Campy NR or SR, but those new bikes like the Lemond fit a niche, too. I guess it's true - my favorite baike is usually the one I just finished riding !