I'd like to start 3d printing in wax.
Is there a reasonably priced 3d printer that is capable of it?
Am I right in assuming that all I need is to make my own filament and set extruder temperature correctly, or do I miss something?
Yes, you can. But no, you don't need to make your own filament for it, there is one called Print2Cast that you can buy for about 50$/kg.
This filament has the following recommended slicing settings:
There are, however, a few more things to look out for when printing with wax, as it is very soft.
The most important issue is the grip of the extruder wheel. See if other people have used your printer/extruder with flexible filaments. If they were successful in doing that, there's a high chance a wax print will succeed as well.
Bed adhesion might also be an issue. MachinableWax.com recommend 6 coats of hair spray on a glass bed, letting each of them dry before adding the next.
Cooling is also important, as with many filaments. You'll probably have to experiment with that a little as either too much or too little can ruin your print.
Yes, with the proper equipment.
Printing wax filament (at 51 seconds): https://youtu.be/tibkVZB_n9c?t=51s
There are also options for melting wax, filling a heated reservoir head, and printing with that. I recommend doing this with a cold ambient temperature, so that the wax solidifies quickly. There's no point in just printing a puddle. :)