I was using a fresh belt and moving the blade back and forth. I don't think this was related to abrasive wear, but it could have certainly been related to lack of technique. The belt is not tight against the platen, so that could have been the problem as Prometheus pointed out. The belt sander is really fast and mine is pretty loud, so I found it a little intimidating. Keep in mind that you can put your own custom platen on the sander if you want a hollow grind or if you want to try to make a slight high spot. I suspect that if I had tried all these things, then my $100 Ryobi sander, which is very similar to the Delta, would have work fine.
My theory here is that with a 1" belt and a 2" blade, you can put the belt in the middle of the blade and grind away more material in the middle of the blade to compensate for not removing material at the edges.
Yes, that was my thinking as well and is why I got a 4" instead of a
1" belt sander. I haven't tried a 1", so I can't compare.The main thing to keep in mind with the belt sanders (and possibly the grinders) is that using those tools is a pretty "rough" operation. Basically you are just trying to get the bevel close and then clean it up by hand. One reason I have been investigating hand grinding techniques is because you can put the blade in a honing guide and get a more accurate bevel. That seems to be true for me, it is just slower than the power tools. That said, the Robert Sorby belt sander that you provided a link too looks really good. If it were available in the US, I would definitely consider it.
On other thing I forgot to mention is that you could look into a hand crank grinder. There are many pretty many for sale on EBay. There used to be a company called Prairie Tool that made them, but I am pretty sure they are out of business. You might also be able to make a grinder. Lee Valley sells mandrels for this purpose.
If you are really trying to save money, I'd really look into a course silicon carbide bench stone and give that a shot. No matter what you try, I think it is important to just stick with that method until you learn to be proficient at it. (I wish I could follow my own advice.)
Mark