It should not be costing you that much especially if your business is less than 20 people at each location.
If you have similar firewalls, real firewalls not rented hardware from the ISP company and static IP addresses you should be able to configure a site-to-site VPN within a few minutes.
Recommended firewalls for each site if you are renting your firewall – Fortigate Fortinet 60-E roughly $500.00 Ea. and can be configured within a few hours by any IT professional worth their weight. Additionally, if you are not paying for static IP addresses these firewalls can still be configured with a site to site VPN using the Dynamic Domain Naming convention.
If you let me know which Firewalls you are using at each site I might be able to better direct you.