There are plenty of ways to spend a lot more on a musical instrument - buy a decent saxophone, or a Moog One! I just found a ukulele online for $1500. The OP-1 seems overpriced because it's very small, but that's also the whole point of it.
I also agree that the current price, while high, is not leagues above what other music gear is priced at. Take a single synthesizer, a sampler, add a keyboard, a sequencer, effects pedals, and a mixer and you can easily exceed $1000. The OP-1 has multiple synthesis engines, multiple sequencers, multiple effects, and sampling capabilities (you can even sample from FM radio, sound familiar?)
While the OP-1 may not win awards for any one of those features, it does unify all of them into a portable package. The OP-1 has also served as a gateway drug for me. I've since purchased even pricier synth gear :)
$1300 is a nosebleed luxury price tag for shoes, but it's a junker car.
But for a synth? Yeah, wouldn't blink. Musical instruments in general have personality, and they cost what they cost.