Price suffix from category

functions.php

<?php 

class studiowp_single_product_price_suffix {

	private $suffix;
	private $category_id;

	/**
	 * studiowp_single_product_price_suffix constructor.
	 *
	 * @param string $suffix
	 * @param int $category_id
	 */
	public function __construct( $suffix, $category_id ) {
		$this->suffix = $suffix;
		$this->category_id = $category_id;
		add_filter( 'woocommerce_get_price_html', array( $this, 'woocommerce_get_price_html' ), 10, 2 );
	}

	/**
	 * @param string $price
	 * @param WC_Product $product
	 *
	 * @return string
	 */
	public function woocommerce_get_price_html( $price, $product ) {
	    $categories = $product->get_category_ids();
		if ( in_array( $this->category_id, $categories ) ) {
			$price .= $this->suffix;
		}
		return $price;
	}

}

new studiowp_single_product_price_suffix( ' na miesiąc', 17 );