Buyers and sellers should realize, however, that the market is quite diverse and should not feel in any way restrained by these prices. HPs tend to be expensive at eBay and more reasonable at flea markets, forsale newsgroups etc. There is no price guide for these items so shop around. Prices vary greatly but tend to be much higher on the net. Circular devices in metal casings like the Fowler tend to cost more and the cylindrical models can cost hundreds or thousands of dollars.
Calculating machines vary from free to thousands of dollars depending on model and condition.
I don't have pricing data on specific models but four function calculators generally sell for much more than adding machines. Most HP calculator and software manuals are now available on CD . Items that aren' t on the CD either aren't in my possession or are missing because I don't have permission to copy them. If it's not on the CD, check your local used bookstores. Batteries were easily obtainable until recently.