I haven't had an opportunity to use Kamui chalk, so I can't speak on how well it performs. I'm kinda dismayed by some of the emotionally charged responses, especially if the US Seller is looking for sincere feedback, he/she may simply dismissed all responses based on a few.
I don't see the dealer holding a gun to anyone's head and forcing you to buy this product. If you think its not a good deal, then don't buy it. If the dealer were able to change the rulebooks. ie. Get BCA and APA to all ban other all other chalk and make it a mandatory purchase, then thats a different story. Right now, we're are still a free market economy, and you vote with your wallet.
On Price
A gross of Masters retails for $19-$20, without shipping and handling.
http://www.seyberts.com/products/Master_Gross_Chalk-935-44.html
http://www.poolndarts.com/p-3150-Blue-Master-Billiard-Chalk-Gross/
So, I can get 144 pieces of Masters for one piece of Kamui. If I lose ,give or toss away a piece of Masters away, each and every day, a gross could last me as little as 5 months.
Exchange Rate
Right now 100 yen is about $1.23, or 80 yen to the dollar. So, being that this product is made in Japan, and was marketted to the japanese consumer, the product may be reasonably priced over there. However, due to the unfavorable exchange rate, its at a price disadvantage over here. If the exchange rates goes to 360 yen to a dollar, I'll re-evaluate.
Being Greedy,
If this product was selling for 100 yen, and the US distributor was marking it up to $25, then I would agree. Can anyone show proof of price gouging?
On Performance
I read somewhere here that a pro was able run over 50 balls without chalking. I can't run 50 balls in a row. Will this make an APA SL3 a 50 ball runner, or allow a 50 ball runner to consistently make 50 balls?
Using a car analogy, there is no sense for me to spend the extra money putting V-rated tires (149mph) on a Ford Pinto that can barely reach 75mph. If this was a Corvette, then not using V-rated tires is suicidal. I don't recall where, but the dealer stated this chalk isn't for everyone. So, are you a Ford Pinto (SL3) or a Corvett class Pro level player?
Being innovative
As John Barton and others pointed out, its not chalk, or what we're used as chalk.