Here is the definition as put forth by the Knifemakers' Guild.
The term, "Handmade Knives" shall mean those knives that are 100% made by the maker, in the maker's own shop using his or her own equipment. Notwithstanding the foregoing, the following shall not disqualify a knife from being a "Handmade Knife":
Embellishments, including engraving, scrimshaw and carving;
Assembly items such as screws, pins, balls, washers and bolt sets;
Heat treatment;
Precision ground, mill run and Damascus bar stock and sheet stock;
Collaborations between Probationary, Voting and/or Founding Members.
What is meant there is that the embellishments and heat treatment can be done by others. The makers don't have to make their own screws and such. As far as collaborations go, it doesn't matter to me if the makers are members of the Knifemakers' guild or not. I consider the collaborative work between makers to be just as much a custom as a single author knife.
There was a time when I didn't accept knives largely made by CAD and CNC to be custom knives. This is no longer the case. I now consider these tools to be like any other and acceptable to be used in the making of a knife.
There are actually quite a few inexpensive, high quality custom knives, so you don't have to spend money hand over fist. However, it is not difficult to spend huge sums on just one knife. If you are interested in folders you will find that the entry level pricing is generally higher than for fixed blades. In general they are more complicated and time consuming to make. You can find quite a few nice custom fixed blades for under $200.00. There are not very many custom folders for under that price.
For most, it means a knife created by a single maker - as distinct from factory production knives.
