Tiffany’s have managed to make themselves a name and therefore are able to over inflate their prices considerably. There are now so many fake and lookalikes on the market, everyone is basically wearing the same.
For a special anniversary, I wouldn’t choose something you might be able to see on your neighbour. I would get something custom made, so there is only the one piece made for this special person and no-one else.
There is also a list with gemstones that have been associated to anniversaries and a piece of jewelry, set with these gemstones, always makes for a very special memory.