Can you make your own epoxy grout?
echo Michael.  I've used Laticrete's SpectraLock..  There's a lot of engineering there to allow water based haze removal (OK, you do need to add white vinegar, very cheap and non-toxic).  Spectralock installation

Off-the-shelf epoxy is going to require a solvent based haze removal (usually lacquer thinner, acetone, or alcohol)..  much more hazardous (indoors you'll need an organic respirator) and adds to the cost.  Checkout West Systems how to use instructions and videos.

Its doable, but...how many experimental batches are needed to verify proper resin/hardner.filler(grout) ingredient mixes so you get a mix that looks and performs like you want..  There goes your savings..  

In the business of grouting tile?  might be worth it.  Doing a one off for a kitchen/bath..  buy a product backed by a warranty, videos, other users (like John Bridges' forum).