There is a half on the same day as the Amsterdam marathon - from the website it looks like the mara is in the morning and the half in the afternoon. There's such a range of accommodation options there's likely to be somewhere within budget, especially if you're organised to book far enough in advance. No hidden costs either, as far as I can see, such as medical certificates, which can be an issue for French and Italian races.
Whether the race itself is any good, I'll tell you on 22nd Oct...