We go through quite a lot of the bought stuff in our house as himself prefers his daily sarni's with mayo to butter, and I like it with chips and with my bean burgers! Maybe I should make it more frequently..
Absolutely agree that the base ingredients are inexpensive, one egg yolk to 1/4 pint oil is the ratio I use; so I keep the volume small enough to use quite quickly.
It's actually easier to use a hand held pestle and mortar for smaller quantities like that - I have a glazed one from Spain called a 'Mortero' (got in a charity shop) that is perfect - ie: designed for the job - for pounded sauces and emulsions. No doubt you will have something virtually identical from South America.
Takes a little care and attention (got to keep those first drips of oil sparse while working them into the yolk) but all that long and it ends up being far far less messy to clean than a blender or other 'bitty' kitchen tech.