The standard response about value is "whatever a buyer is willing to pay".
These are rather a small niche market among collectors, having no content of musical or personality interest. Someone interested in the history of speech therapy might want them; but they are not generally sought after.
Aside from that, condition is also a factor. Are they mint condition, or do they have issues such as mold, scratches, cracks, etc.?
Your best bet would be to put them up on eBay at a modest initial price, and wait to see whether you get any bids.
Last Edit: Aug 24, 2017 0:47:20 GMT -5 by lucius1958