There is plenty of variation in density and hardness between trees, and from what I've heard, even within the same tree. The numbers available on the internet are only an average, and many of those averages don't have a large sample size. I think most of our perception of woods comes from anecdotal evidence. If you look at this well-informed website and its articles, you will find that ebony doesn't even crack the top 10 hardest or densest woods. https://www.wood-database.com/wood-articles/ The author of that website has a great video that explains the variations and expectations of exotic woods. Also, check out his modest collection of books. 😉 For those disinclined to dig too deep, the short version is: There are many smaller and lesser-known species that are harder and denser than Lignum and the other top contenders There are several species in Australia that are slow growing dry climate trees that are an ironwood variation or similar. The size and availibility just isn't the same as with ebony or blackwood or lignum of years past, so they don't enter into the conversation for us laypeople. Regarding instrument building, how hard and how dense do you need? I don't know the answer, but I would guess that any of the common woods used for guitar fingerboards would easily fit the bill, and be relatively easy to work with. Katalox and granadillo (not to be confused with grenadilla) are plentiful and more budget-friendly, among many others. Ebony is not restricted in musical instrument form, and most of the rosewoods (Dalbergia) are okay to ship in musical instrument form, as long as they are declared properly. Messing with ivory, even mammoth, and Bolivian rosewood are not worth it in my opinion. Avoiding all the dalbergia species if possible is not a bad thing to do. There are plenty of materials with similar or better mechanical properties that work just fine, and don't carry risk.