Solution:
Make use of the snippet below on change of the amount;
jQuery( function( $ ) {
// Run on selected variation price change.
let currency_symbol = '£';
for ( let i = 0; i < $( 'p.price' ).length; i++ ) {
// Define the subtotal block.
let sub_total = $( 'p.price:contains(Subtotal ' + currency_symbol + ')' );
// Define the condition for the finance block.
let amount = Number( sub_total.text().split( ' ' + currency_symbol )[1] ) >= 400;
// Show or hide the finance block based on the condition above.
amount ? $( 'div.finance' ).show( 'fast' ) : $( 'div.finance' ).hide( 'fast' );
}
});