There are a lot of possible variations on this, I chose to keep the battery outside the box so I could pop it in and out rather than use a separate on/off switch. Another capacitor or a larger one can be substituted and voltage set lower to increase total joules potential but I have found 1000uf at 35v to be just right for welding silver, nickel, nichrome and kanthal 28-34g wires together. Really any old power supply can be substituted for the battery as long as it is within limits of the input voltage for the LM2577 board, I just have 18650 lithium ion batteries always charged and on my nightstand so it is convenient for me to use this form factor.
The cost for the components is right around $25. You can buy bulk wire for about $25 for 250 feet. Commercially available resistance/no resistance wires are available for $1ea and measure 3" long. So with the same $50 investment and a few hours of your time you can make 1000 wires for what it would cost you to buy the pre made ones. Plus, by building your own, you have control over what wire gauge, what material, and what resistance the final wire will be.
This is not my original idea, nor is it the only way to make such a device. This is simply a illustrated guide to build one the way I built mine.