I'm not sure what you mean by disproportionately (proportionate to what?) but yes, the trade with japan was extremely successful, for a while.

But, first, let me elaborate on why they were there in the first place. It wasn't because of the insatiable Dutch appetite for Japanese goods. One of the problems that the VOC (the Dutch East India Company) faced was a trade imbalance, they needed constant infusions of silver from Europe (and the Americas) to buy Asian products for the European market. The solution they came up with was to trade within Asia, and use the profits to pay for the trade with Europe. Japan played an important part in this plan.

Asian products (like silk from China) sold in Japan provided the company with vast quantities of precious metals. I don't have access to my source (Dutch primacy in world trade by Israel) any more, but according to my notes the top year was 1639 when almost 7.5 mln guilders worth of precious metals came from Japan, bringing them close, but not to, their goal of independence from European/American silver.

However, the amount of silver, gold and copper leaving the country worried the Japanese, it was being exported faster than it was being mined, so there were increasing restrictions on the trade. Added to that, the loss of Taiwan in 1662, and the unstable situation in China around that time, meant the VOC had a harder time getting hold of Chinese products (though Persian silk provided some solace). This meant that the importance of the japan trade decreased gradually over time.

If you can find a copy, F.S. Gaastra wrote an article on the VOC intra-Asian trade in The emergence of a world economy