You can’t justify acoustic economically unless you make your income from the piano. Aesthetically acoustic is the clear winner, but you’d better have your pocketbook well stocked.
Personally I prefer electronic because I’m not a trained pianist and I appreciate the versatility of something like a Korg Kronos over the undeniable physicality of a concert grand. And I splurged a bit on my audio setup so I can still get some good body resonance going when I don’t mind potentially annoying the neighbors.
At 2% inflation, a series of 5 purchases (one every 10 years) totals to 27815 GBP
On Yamaha today, that will get you a 6'1" C3X.
I don't have great knowledge of the market for second hand midrange Yamaha grands but if it's well looked after (which as discussed costs money) the value of the piano will not be zero.
A spot check on gumtree[0] suggests that a well maintained 30-year old 6'1" Yamaha C3 is worth 50% of today's C3X. I'd be more confident that a well looked after Steinway B would command a decent price - especially if you picked up a decent 5-10 year old to avoid the premium associated with newness then sold it a few decades later.
So for me, I don't agree that the economics of buying a grand piano are as clear cut as your post makes out but I agree that periodic upgrading of a DP is definitely viable and gives you more flexibility.
I used to be really fascinated by antique pianos (Bechstein and Steinway) and I was really impressed how gradual their value decline was, but also how nice they can sound. A well looked after 1900s Bechstein sounds so beautiful.
[0] https://www.gumtree.com/p/pianos/yamaha-c3-conservatory-gran...
Given that it is allegedly from a conservatory I'm willing to give the benefit of the doubt that the piano will be well used but also well maintained.
I’m pretty comfortable in my belief here. Certainly the immediate winner is the DP, and you may not stick with it long enough, or even live long enough, to win the long term bet you are making here.
Back to my original point — I’m not saying the acoustic isn’t worth it, simply that you should not analyze it from a purely economic point of view, because it is a losing argument from that perspective.
I also can accept your reasoning and definitely agree re. time value of money (and the value of optionality) but I was surprised actually see the numbers play out the way they did.
As for me, the much bigger problem is finding a place big enough to house a bloody grand piano!
But IMO fixing an action or motherboard on a 10+ year digital is much scarier than fixing a purely mechanical acoustic. A well looked after acoustic has a reasonably forgiving depreciation curve if it's a decent brand too whereas I picked up top-end digital for 45% discount even though it was less than a year old