According to linked answer, the maximum duty free allowance is roughly half of this amount. But this would only count if you bring it for personal use. Since you're bringing it unopened, the customs may assume you intend to resell it, and thus not consider it eligible for personal allowance. This customs decision could be appealed, but the process is generally expensive, cumbersome and slow.
Of course there is always an option not to declare it. But in this case, if caught, you can be charged with smuggling. This is considered a serious offense with possible criminal penalties, and at the end may cost you more than the full duty price on the phone.