Brakes Broke? My maybe heart-and-wallet breaker?

I've looked, and seen other Prius owners with brake issues, and know there had been a recall on some models (not the V, unfortunately, as far as I know). Problems with the accumulator / pump, and sometimes the master cylinder assembly. It's kind of hard to justify putting $3,000+ into my 2013 Prius V if it comes to that, but I'm not sure of what other options I've got.
I was dumb enough to buy the car a few years ago from a local OffLeaseOnly sales place, and asked about the buzzing noise (about 3 seconds long, followed by approximately 9 seconds of silence, repeatedly) and foolishly accepted "that's normal". The car always does this when I enter it (with the remote key), even before touching the ignition, and will continue for 10 minutes or more (still without touching the start button). When driving, the noise can continue indefinitely. Recently I began getting the dashboard array of brake warning lights occasionally (skid/traction, (!), ABS, brake). I now traced the familiar noise to the accumulator/pump unit (presumably from the pump actually running intermittently). The warning lights are solid (not flashing), and shut off after several seconds (but stay on for increasing durations), and have not triggered any pending or existing Diagnostic Trouble Codes on my OBD-2 scanner. I see no pattern to when/why they illuminate or turn off, but the feel on the brake pedal is definitely changed (loss of power braking) while the lights are on.
I'm guessing the accumulator's pump is (finally) beginning to fail - no longer able to stabilize / equalize the pressure in both segments of the system, and this is causing the lights to come on. Why no DTCs though seems odd. From other postings I expect a C1391 (brake accumulator leak), C1345 (skid / traction warning), C1256 (low accumulator pressure), but I haven't (yet).
I'm looking into getting an official diagnosis and repair estimate, but have seen from other postings it will be quite expensive if it is the accumulator/pump assembly.
Any advice would be appreciated!