Tri-X has more than that. 1.5g per square meter is more like for modern microfilms, copy films, lith films, etc. and modern printing papers.A standard (old technology such as say, Tri-X) film has, as far as I get it, a silver content of 1,5g per square meter. The same content of silver could also coat the same amount of paper. I am not sure of the Ag content of T-grain films but I believe it is lower due to some manufacturing differences.
First of all, there are lots of films that use 3g or more. But in light of post-1950 emulsion technology (it doesn't have to be state-of-the-art or anything) silver content is merely a marketing hype that is used by some authors and retailers these days. And I don't even think the authors or retailers know the actual silver content of the materials they are talking about. Plus, older emulsions contain a lot of crystals that are not even sensitive enough and they just consumed silver and processing capacity of the chemicals. So, even if a product is indeed silver-rich, it just means technology-poor.What I am really trying to figure is this idea of "silver-rich" materials. Let's say one makes a film with 3g silver per square meter. Apart from the obvious rise in costs, does it make any sense altering the levels of silver - and is there any limit to how much you can use in an emulsion?
You can put more silver in the emulsion if you want. But only the crystals near the surface get exposed and the bottom ones won't even get exposed enough. Also, if you put too many crystals, they increase light scattering and decrease resolution. Modern tabular grain technology and double layer coating allow a much better tradeoff of these competing factors.
In paper emulsions, the resolution is inherently low and also irrelevant, so you can add more silver with relatively little harm but it is still unwise for the same reasons.