Depending on the stock list it could be well worth over 5k I lurk on some salty forums and you would be shocked at how much some people drop on a single coral frag. 180g is alot of coral space and it looks rather filled in, even more common corals you are still getting quite expensive.
Seeing as it is in a tattoo shop, "assessed" maybe he has it maintained by an outside source who does maintenance on the tank and asked how much it would be worth in their shop.. 10k for a healthy established salty tank doesn't seem shocking depending on what is in it and all that or maybe he started with barley anything 18 years ago and now it is completely filled in so he asked a shop how much the corals would be worth now days. Just guessing though *shrug*
Some of those corals would go for 100$ alone. The bigger they are, the more they are. A small rock (about the size of my palm) with about 6 mushrooms on it cost me 40$ and those are the cheap ones..