 Owing to the high cost, the two heights in question will be treated as “the same for present purposes”, and if one of the trees is tall, so is the other. In effect, the application of ‘tall’ is governed by an interest-relative form of tolerance. (Presumably the speaker’s interest must invariably be in cost whenever he considers saliently similar values; in particular, the latter interest cannot be superseded by a different one, like, say, an interest in the location of the sharp boundary.) 