Providing advice and guidance on the replacement costs of engine mounts is extremely difficult because of the many variables that influence such costs. Many factors influence engine mount replacement costs, and although the cost of the affected mount is an important consideration, the most pertinent factor involves the amount of labour required to remove and install some types of engine mounts.
In some cases, a professional mechanic might be able to replace some mounts in about one hour, while in many other instances, a mount replacement can take several hours and even an entire workday. Exactly how long a mount replacement will take depends on the vehicle and the type of engine mount that is involved, but most importantly, on the location of the affected/damaged engine mount.
Note also that there may be other costs involved. For instance, it might appear as if only one engine mount needs replacement, but it often turns out that one or more other mounts may have been damaged because of bearing the loads the failed mount should have carried. If this turns out to be the case that a workshop must replace several mounts, the total labour costs alone could run to several hundred dollars.
As a practical matter, though, most simple rubber mounts can be had for less than about $100 from some online retailers, while complex hydraulic and active mounts can run to about $300 or so from most online retailers. However, while these prices might sound reasonable, be aware that there are no guarantees that engine mounts bought online will perform as expected. Thus, the better option is to source engine mounts from authorised dealers or from trusted and reputable vendors that supply OEM-equivalent mounts that are guaranteed to work as expected, although OEM and OEM equivalent mounts may be more expensive than most aftermarket mounts.
Also bear in mind that labour costs depend on your location, as well as on the vehicle, with most workshops charging higher rates for complex work on imported European vehicles, mainly because European vehicles are generally more cramped and difficult to work on.
As stated elsewhere, labour costs to replace engine mounts vary greatly, so we strongly recommend that you consult with several workshops in your area to obtain price estimates that include all possible and likely costs. At a minimum, such estimates should include the cost of inspecting all the damaged, worn, or defective mounts in the vehicle, the cost of replacing each damaged mount, as well as all the fees, taxes, and levies that are payable in your location. If you live in a remote location, make sure that the price estimates you obtain also include accurate shipping costs of all the parts that are required to complete the mount replacement.
So, given that replacing some engine mounts on some vehicles could potentially cost up to $1000 (or more, depending on the vehicle), we also recommend that you research the costs of replacing the same engine mount on your specific vehicle before committing yourself to a repair that could cost more than you expected, or are willing to spend.