How far in the past? When I was building bases for a local taxidermist, before the world went stupid, I had $150-$200+ in material for most of them, usually alder; typical base was an octagon. Add my day's labor in, and his price was between $450-$600, depending on the specific design and wood. He only added to that if he created habitat on the top. Simple routed bases for birds were $40-$80.
When I priced the same lumber this past summer, I would have close to $250-300 in material in a typical octagon (24"Wx30"Lx28"H). Obviously this changes a great deal depending on the size of the base, but hardwood lumber has truly gone stupid in price.
I've seen a few bases that originated in SA, I believe you will find having them built in the US a better option (can't speak to the shipping cost from SA). My bet is, you can find a good custom cabinet maker locally and get what you want for a lot less than the $4-5k you mentioned. While I haven't seen one in person, the pics I've seen of the bases
@gizmo has made for others here on AH show quality work. Might be worth getting in touch with him if the MD cabinet makers are overpriced.