My comments would be unless you have a means or "partner" to convert to production, there isn't a point. The partner could be overseas. I'm also not sure if there is a demand for a "limited" production prototypes. e.g. some trinket that would be be made for a trade show etc.
I think Polycase did something interesting. They don't require a lot to "customize" an enclosure for say drilling and labeling. I may decide to sell something on ebay once I get it developed, but the absolute most I could sell would be around a 100 because of the availability of an obsolete part. I am using a Polycase enclosure. It's much bigger than I would like, but a custom case could make it much smaller. It is, in essence, a "remote control" for an obsolete, highly in demand product. The units sold on ebay without a remote goes for $100 less. One guy I talked to said he would be willing to pay $150 for a remote. That's a lot of dollars. It would not be a lot of profit.
Buttons are like $2.00 each x 13 ($26), Case is like $16, label is like $3.00 not including punching in printing. Tools to punch are expendable too. That's $45 right there and no supplier shipping.
Costs add up quickly without "economies of scale". I don't have the means of drilling the enclosure: about 14 holes all the same size, but one. Punched, non rectangular, labels are just as bad. I can make 3 labels at home for about $10 for 3. I did have a commercial label made for $20 each that were not as good as mine. The outline was hand cut and they didn't punch it either.
It would be a hobby and not a business.