const products = [
  {
    id: 1,
    name: 'butter',
    price: '5pln'
  },
  {
    id: 2,
    name: 'bread',
    price: '4 pln'
  },
  {
    id: 3,
    name: 'eggs',
    price: '3'
  }
];

const getTotalPrice = (totalPriceSoFar, { price: nextProductPrice }) =>
  totalPriceSoFar + +nextProductPrice.replace(/(\d+)(.*)/, '$1');

const totalPrice = products.reduce(getTotalPrice, 0);

console.log(`Total price of products: ${totalPrice}`);