While it varies on a case by case basis, pricing starts at $18K USD for the entire setup (Trust + LLC) for the first year, followed by $9K USD annually in maintenance fees. A bank account introduction, if necessary, will run you an extra $2K USD.
We usually recommend you have at least half a million dollars in assets in order to justify the cost of establishing and maintaining an asset protection trust, but we've seen them established for less.

One thing is for sure, the more you have, the more important it is!
It doesn't really matter. Both are excellent at protecting your assets and have nearly identical protections. Both will protect your assets immediately.

The main difference is that the Cook Islands will leave a 2 year window open for someone to "challenge" the transfer of your assets into the trust, before they shut that door completely. This challenge is not only a costly endeavor, but also practically insurmountable (the person suing you must physically travel to the Cook Islands to submit a claim, and also prove beyond any reasonable doubt, aka 97%+ certainty, that you moved assets in the trust for the express purpose of defrauding him specifically).

Belize? That door is shut from day one.
Don't bother. There's a reason that the vast majority of trusts are established in either Cook Islands, Belize and Nevis. They are impenetrable. 

Unfortunately Nevis has become very difficult to deal with, and the attorneys we work with do not recommend it anymore. The former two however are stellar, and currently the gold standard in the offshore asset protection industry.