$400 - Real Oscilloscope
$90 - USB Oscilloscope like the T-train
$40 - GRJ with 4 LEDs with fixed Rs and comparators
$10 - Adrian with 1 LED and trimpot tuning
I think the market is pretty much flooded at this point?
Agreed. Just suggesting that if the journey is to learn DipTrace and the process of fabricating PCB's via OshPark, it's always useful to bring something to the party given GRJ has already done the heavy-lifting on the $10 version. So this would be, say,
$11 - Adrian with 2 LED and trimpot tuning