The cost seems reasonable to me - parts cost may go up if the strut bearings have failed as well as the mounts (same labor). A bad bearing might become evident only after the strut is removed.

One question is whether both sides are really bad. I replaced one front strut mount a year or so back, and the other has shown no signs of failing so far. I am sure it will but I did not see good sense in replacing it beforehand.

Similar for rear shock mounts - I've replaced both, but at least 3 years apart.

Some pro mechanics will not want to do just one side - and in truth you may have both sides bad. You can lift the hood and wiggle either strut mount. The one that is bad will wiggle around very easily.

This would depend on your budget, but I personally would not replace the struts themselves unless one of them is actually broken or leaking. They do soften over time but so does everything else in this world. In the case of struts, replacing just one is not a good plan - car would likely ride and handle very unevenly.

An additional common source of front end noise is loose or broken stabilizer (sway bar) links. Your tech probably checked for this.