In what now seems to be a past life I worked as an S/E kitchen designer fitter. At the time I could not afford one of the few worktop jigs available as most came with a router, I already had one. My approach was to make a jig of melamine faced chipboard, cheap relatively easy to work and comes with its own notepad, at least in white. The jig was basically a slot a little over 650mm long with an extension at 45 degrees about 40mm long. The width of the slot was designed for a 16mm bush and a 1/2" cutter, and from memory was about 40mm wide. I cut the slot with a jigsaw, slowly, using a blade with no set. The radius' at the corner of the Mason's Mitre were taken care of by the guide bush in the router base, the 15mm chipboard was just about right for the bush axial length and the maximum length router cutter I could get hold of. The melamine surface was useful as the base of the router slipped easily over it. Now it needed care in setting it up, using G-Clamps etc. but worked surprisingly well over about 70 or perhaps 100 kitchen worktop joints, and only fell in to disuse rather than becoming worn out or breaking. Perhaps it was a little awkward to set up but then the saving was worth having. If you decide to make one rather than buy you will obviously need your own 'How to use' instructions. Don't forget the rotation of the cutter in the router, one half of the joint will probably need to be cut from the underside of the stock. My jig was not big enough and I had to make a separate jig for the routing of worktop connector slots, a little more planning would have put both jigs into one piece.