I guess I can be a little more generous with the Casio AP-25. I've had one for about 3 months now and I've gotten to know its abilities and limitations.
As a beginner's piano (possibly a substitute for those shrill but inexpensive Korean uprights), it's quite a bargain at $799 (available at Costco). It's "maximum" polyphony of 64 notes is available only with the Grand Piano 2 voice which is a smaller sound sample (so it uses less memory). You can almost tell the difference in quality with the speakers. You can DEFINITELY tell the difference with headphones.
The sound samples seem just a hair's touch below Yamaha's when heard through headphones. Through the speakers, there is no perceptible difference versus the Yamaha YDP-121. The Grand Piano 1 sounds a bit boxy (but that's the same with any digital that has its speakers pointed downwards). The Piano 1 sample is brighter and is good for jazz.
The graded key weighting is split about down the middle and almost imperceptible unless you have a sensitive touch.
The AP-25 has only two pedals (versus three on the Ap-28 and on the Yamaha YDP-121/YDP-223). The soft pedal can be switched however to sostenuto if you need it. I seldom use the sostenuto.
As an entry-level learning piano, it's probably a better value than the YDP-121 (and it has MIDI in-n-out too). As a performance device, you'll need to spend more than your current budget.