It really depends how you see it. If you're looking at the Internallnal retail price, the Onkyo is no cheaper than the ak300. Will it sound better? Perhaps. That's Subjective.
But what I think most people fail to consider is this. I've spoken to a lot of retailers and distributors in my country, and they admit, that the products from astell and kern have by far the best track record in terms of durability and consistency. A couple of the local retailers actually offered the Onkyo dp-X1 for sale, but the RMA rate was so high (up to 40%) that they just gave up after 1 batch. Other Brand’s have problems of SD cards getting stuck and what not. Of course not everyone experiences this, But I think taking the retailer's experience into account is the most objective way of assessing this.
Also, another thing is the finish of the product. Even the Onkyo, which I will argue has the best finish after AK and cowon, really doesn't convey the same sense of immaculate construction as the AKs. The new cowon a are catching up, but still, AK is some distance ahead. In terms of the smoothness and stability of the UI and the firmware, retailers have also reported that AK has been giving customers the least problems.
Don't get me wrong, I'm not an AK fanboy. I don't have a single AK product, and I think they're sorely overpriced for th sound quality. But AK isn't just about sound quality, and if you take everything into account, I can see why they're priced above the rest.