What is a strong joint for 1/2" ply drawers? These are going to be
relatively large drawers; 30" wide x 12" high x 28"deep and will carry
a good bit of weight in them(power tools, parts, etc. Nahm uses a
dovetail jig but it's out of my price range. I have to make about a
dozen of these drawers so the joint has to be relatively easy to
reproduce.

I know many folks will probably suggest fancy joinery, but I've made dozens
of drawers with simple butt joints (sides overlapping front and back) and
they have held up very well. Many of these are loaded quite heavily.

I prefer to use 3/4" ply for the front and back as it gives more of an edge
to glue and nail into. I use 1/4" plywood for the bottoms set into a simple
dado. I use a router bit that is undersized to match the true size of 1/4"
plywood, so the bottom doesn't rattle around in the groove.

I typically use inexpensive 3/4 extension Blum drawer slides, but did use
full extension slides in my computer desk.

If you insist on using a more advanced joint, you could try a "Drawer
Lock" router bit (92123 or 22637 at Rockler for about $35).

Anthony