Speaking from 6+decades as a former custom builder, competitive shooter & avid collector of antique firearms, yes these can be a very good investments if your experienced with shooting antique firearms.
If not well experienced in collecting & shooting, buy from a trusted source or get advice from someone who is qualified.
** I Personally do not shoot antique firearms that are in mint condition, those get sold to collectors who just display them.
Bottom line, the decades of thrills wife & I have had at rendezvous, hunting, & competing with historical firearms far exceeds any thrills I've had over making a fast buck.
*I do not recommend any of the above to those who are not prepared to provide meticulous care of historical firearms for the next generation to enjoy.
Relic shooter