Mine mammoths

The number of individual mammoths preserved in Siberia is something like half the human population of the US. Some are presumably not in good condition. However, right now many of them have been used for ivory with the problem that elephant often gets passed off as mammoth.

In historical times, mammoth meat has been eaten. The largest weigh about eight tonnes. They are, of course, made of skin, bone, hair, ivory, meat and so on. Much of this is usable and has been used by people a long time ago. Similarly, woolly rhinos have substantial amounts of horn, which has a similar issue to ivory.

Russia is not doing well economically but has a whole load of this natural resource. Leather can be tanned using the biological materials present within the body of the animal such as the brains (mammoths have relatively large brains relative to their size) and the dung (a whole lot of dung in a mammoth colon, i suspect). I couldn't swear to this but it seems likely to me that many people in Siberia already have the skills to make leather in the traditional rather than the industrial way. They also presumably have a lot of other skills which enable them to use mammal carcasses efficiently, currently applied to the likes of horses and deer.

If they were to apply these skills to mammoths and woolly rhinos, there would be a considerable advantage. The products could be labelled as cruelty-free (though of course they wouldn't be as life is inherently violent), they would also provide an income for people understood to be indigenous and in need of economic support - that combination is particularly appealing to certain potential consumers - and since they would effectively be using a non-renewable resource, it would have a natural scarcity which would make it more profitable. It also provides the Russian economy with another source of income.

The problem is others passing non-extinct elephant and rhino stuff off as this stuff. That can presumably be addressed by something like amino acid racemisation dating, since most surviving mammoth and woolly rhino remains are of such an age as to allow that method and the temperature of the permafrost would either be established or easily ascertainable, allowing a high degree of accuracy. That same racemisation would render some of the products more resistant to decomposition.