Dunno - when starting out with a 6MP pro camera sensor (not a P&S camera - an SLR), I haven't seen a difference in image quality (after a basic color/density correction) between a high-end lens and a more inexpensive lens.

I'm NOT talking about a $50 generic brand lens - but something of the $200 variety compared to $900 variety is not going to give you significant enough results to differentiate between them when the image's long side is scaled down to 1024 or smaller.

Any chromatic abborations disappear enough to be ignored, and even slightly softer images look sharper when scaled down (it's an optical illusion based on the fact that there isn't enough distance/pixels to define the sharpnes of edges - or lack thereof). A good (inexpensive) lens shade will take care of most of your bouncing light needs (which you should be using for expensive lenses as well, regardless of price) giving you richer color and contrast.

While you shouldn't reach for the cheapest lens on the shelf, if all you're going to do is web imaging then don't worry about trying to afford the most expensive ones on the shelf.