We understand these are quite commonly replaced, however motor mounts present a few difficulties that make estimating very difficult, and therefore unreliable. The issue is that there are up to 3-4 mounts that are unique to every engine, and identifying the correct part is difficult. There can be a lot of labor overlap when replacing more than one, so these estimates are best left to the shops performing these repairs.
My recommendation is to call around to a few shops in your area, here are a few: http://repairpal.com/euless-auto-repair