RubixML model always return the same prediction in PHP

I’m trying to extract the product price for different sentences using https://rubixml.com/, but it always returns 260, the first label I give to it

<?php
include_once '../vendor/autoload.php';

use RubixMLDatasetsLabeled;
use RubixMLDatasetsUnlabeled;
use RubixMLClassifiersKNearestNeighbors;
use RubixMLTransformersWordCountVectorizer;
use RubixMLTransformersTfIdfTransformer;
use RubixMLPipeline;
use RubixMLExtractorsCSV;

$samples= ['The price is 260','The cost is 500','This shirt costs 300','The value of this item is 450','Sold for 150 dolars'];
$labels = ['260',             '500',            '300',                 '450',                           '150'];

$dataset = new Labeled($samples, $labels);

// genrate the model
$pipeline = new Pipeline([
    new WordCountVectorizer(100),
    new TfIdfTransformer(),
], new KNearestNeighbors(3));

// training with dataset
$pipeline->train($dataset);

// analize new frace
$new = Unlabeled::build([
    ['Price: 1200'],
]);

// Predict
$predictions = $pipeline->predict($new);
var_dump($predictions);

I have changed the values for the KNearestNeighbors, provide larger inputs for train dataset, change the Vectorizer. But nothing changes.