Is there a word for something that has been well-designed, looks good but can't sell. This can be an object or an idea..
As in Concept Car or "This energy neutral house was built from natural materials as a concept."
Companies often build such "concept products" as a marketing excercise and many are very well engineered, though not economically viable and the company has no intention of selling it, at least not in the immediate future.
If they built it with the intention of selling it and it didn't sell it would by definition be poorly designed and would be a White Elephant.
Thanks to Hotlicks for comments. There are some products (such as the Betamax) that whether due to bad luck or poor management, suffer because the market standardizes on the competitor's format. I would like to suggest the term victim of standardization for that.
I'm not sure if it needs padding out as a simile or can be used just as 'It's a Betamax'.
Developed by Sony Home movies, Home video Betamax (also called Beta, and referred to as such in the logo) is a consumer-level analog videocassette magnetic tape recording format developed by Sony, released in Japan on May 10, 1975....
The format is virtually obsolete, having lost the videotape format war though an updated variant of the format, Betacam, is still used by the television industry....
LThe SL-8200 was to compete against the VHS VCRs that had 2 or 4 hours of recording time.
Betamax and VHS competed in a fierce format war, which saw VHS come out on top in most markets....
The VHS format's defeat of the Betamax format became a classic marketing case study.
Diller on Aereo: It's like Betamax.
Is SPB the Betamax of Layer 2? | The Networking Nerd
Commonly used in the entertainment industry is "Turkey" - And I think, although this is not supported in that Dictionary link, that its use can be extended to other things:
"You remember that thing we made? Brilliantly designed but turned into a bit of a turkey in the end"
Another related term is "White elephant" - Again this dictionary definition does not tally exactly with my understanding of the term to mean "useless and impossible to get rid of"
"They spent a lot of time on the design but in the end it was a bit of a white elephant"
I love Edwin's 'Betamax' reference, but I believe a better term would be critic's darling. It's widely used in the artistic fields and sometimes in technology to describe a thing that dazzles the press and the cognoscenti but fails to find a broader market/audience. (Cf. Segway, Jim Jarmusch films....)
A very well designed and well-built aircraft that just never became a commercial success.
While it doesn't imply any degree of quality on its own, a prototype or proof-of-concept might fit the bill: it's an early version of a product which is typically unfit for selling or mass producing, but serves the purpose of demonstrating the design that might be approved for a final product. Because they're often produced for pitching an idea to an investor or board, they can look quite attractive and might even be ready for production. The "ugly" prototypes tend to be those produced for purposes of experimentation, where function supercedes form.
I think Marv Mills' suggestions come pretty close to the best answer.
The word folly http://www.thesaurus.com/browse/folly is used for architecture that is well-designed, but pretty much pointless, but could equally applied to any item that is costly but frivolous. If the item is simply an unnecessary purchase then frippery comes to mind. Perhaps the OP would like to expand or clarify the original question?
looks good but can't sell
This makes me think of a polished turd. Summarizing:
So you've got the job of producing, managing, or marketing something. It could be [...] anything but whatever it is, it's bad, or at least mediocre. The concept is fundamentally flawed, the execution so rushed and so badly thought out, that no one in their right mind would buy it on its own merits. [...] It's your job to make it look good. So what do you do? You try your best to make it look better than it is and hope that it's effective enough to sell a few million copies.
This is a slightly different bent from your question. When you say "well-designed but not commercially viable," I think you're looking for something that is fundamentally a good thing, but held back for other reasons. Perhaps it is prohibitively expensive because it's ahead of its time, like tablet computers in 1991, 1993, et. al. up until Apple successfully marketed the iPad.
But maybe you're thinking of something that's
- more form than substance; more form than function
- all talk and no action
- big hat, no cattle
- marketing success, commercial failure
Then you could be dealing with a polished turd.
On Shark Tank they often refer to these types of products as tchotchkes.