- url = price.new_record? ? prices_path : price_path( price )

.products--prices-form.inline-block
  = form_for price, as: :price, url: url do |f|
    = hidden_field_tag 'price[product_id]', price.product_id

    %label amount cents
    = f.number_field :amount_cents
    = f.submit '>'