v3 bumped the processor to a F7 from a F103, a fairly significant jump, so unlikely to be a cost reduction revision.
Big deal. Yes it's a big jump in terms of performance, but on a cost level, the F7 they used is approx $8 by 1000 and the F103 approx $3.5 (public price, to get an idea). And they probably want to phase the F1 series out of new designs at ST anyway. Besides, I'm pretty sure ST has preferential rates on ST parts.
There is practically nothing else on the PCB apart from a few passives and probably a couple regulators and protections diodes.
Looking at the design only, it could very well cost less that a V2. Or at worst be in the same ballpark.
As for performance, it's obviously going to be much faster, but is that going to really impact use in the field? Maybe for tracing as andersm said. To be fair, V2 or V3, those are low-cost dev. tools at $35. So the pricing is certainly right. Nothing to complain about here.
But still not impressed one bit.