You can use Link4 for free, yes for free. Our Link10 plan is for free if you are receiving 10 purchase bills/invoices per month.
We are sure you will see the benefits of eInvoicing and using Link4 and only then you can upgrade your plan based on the amount of invoices you receive.
The average cost is less than an Australian postage stamp to send an invoice. Go to the Pricing page for full options.