$360 for the tuner and unlimited tunes. Bought a used LM-2 datalogger w wideband O2 and OBD-II plug to record PCM data for $200.

What aftermarket EFI system costs under $600 for the computer, harness, sensors, injectors, etc?

Once the tuning is done, it's done, no need to keep going back once a month, unless you keep modifying your motor. Been 2 years, I've done my truck, and helped 3 others do theirs. Same program writer on all of them. Vacation or sick, that can be worked around, just like scheduling dyno time or track sessions to tune a carb or aftermarket EFI.

If you have the hand held tuner already, the PRP software is $350. So you can pick up the handheld used for about $100, buy the PRP for $350, and an LM-2 for $200. Again, less than $700, and now you're writing your own tunes.