Ok but now Microsoft is pushing silverlight to become the replacement for flash and now you have clients who insist on silverlight. Now you are stuck because you can't do silverlight 3.0 just 1.0... And they want this and that feature which ain't in 1.0.
As long as M$ controls the market, and they do, there will be a reason to pirate. Just as M$ is there to make money they will continue to to conceive of ways to exclude opens source. This can be said for whatever industry you work in. If there is a dominant commercial product that doesn't play nicely with opensource alternatives people will pirate the commercial product because with that they can do more work and actually connect to that dammed blasted closed source server/app...
If you have customers who insist on using silverlight, and that is what you offer but you cant afford the software, then sorry, but your business plan is fail.
You could also use the open source flex SDK, and offer a better product to your uninformed customers, at a far better price.