wc-subscriptions-custom-product-price-string.php

<?php

/**
 * For subscription products, overrides the default product price string with
 * something custom.
 */
add_filter(
	'woocommerce_subscriptions_product_price_string',
	function ( string $product_price_string, WC_Product $product ): string {
		// Update the criteria as needed to target the correct product(s).
		return $product->get_id() === 12345
			? '¥50 every quarter (but billed monthly)'
			: $product_price_string;
	},
	10,
	2
);

Probably obvious, but this is a POC rather than a complete solution. In reality, we might want to do a better job of building the replacement string with the same (or a very similar) HTML structure we see for other products, and we may wish to pull information from product meta data, etc etc.