Welcome to the forum.
We have sold a few 12" (300mm) engraved mirrors to the general public and we charge $49.95 and it takes us about 3 to 3 1/2 hours to do 1 mirror with our 30 watt laser. (full power at 3 ips)
They either like the mirrors or they don't as it's not everyone's cup of tea.
Some sites in the USA charge $99 for theirs.
Mostly we just engrave mirror tiles but sometimes we do mirrors with frames which sell a lot better. People don't want to waste time getting them framed themselves.
Here are some examples of what they are like and it's taken me about 100 hours to get to this stage but I still have some improvement as I don't think they are up to my standards yet. (but getting better)