Simpler ways to generate a negative voltage?
ICL7660 (and similar chips) are cheap and will easily generate a negative voltage. 

Even cheaper, if you have a clock signal around you can use a CMOS buffer to drive a simple charge pump and get ~-3V from +5V. Maybe 5-10 cents in moderate volume.  

Neither of those are suitable for generating 1W, more like 10mA or less but I'm not sure you really need 1W. 

For simplicity nothing beats a DC-DC converter (one part, potentially), but cheap ones tend to have lousy (or no) regulation and can give higher than normal voltage with a light load, so read the specs carefully.  

There are plenty of inductor based switching supplies that can generate your 1W at -5V, as just one example, the LM2576 but there are many others.