Hi Rohrgatz,
There would normally be a manufacturing date on the tag but I can’t see from the picture if the words beside the date indicate the manufacturing date or not.
It would depend on the specifics of the construction more than the name of the manufacturer.
I think that what you are looking at is a foundation not a box spring (a box spring has flexible springs inside it which flex and a foundation has a more rigid support surface with no springs and has very limited to no flex). There is no “average” price because there is such a wide range of different qualities and it could be as low as $50 - $100 for a cheaper foundation to over $500 for a foundation built with stronger more costly wood and a higher quality quilted cover. There is more about the different types of support systems that generally work best for different types of mattresses and some sources for each of them that you can use as a reference point in the foundation post here and the posts it links to.
Phoenix