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not get enough Bitcoin business to justify the effort to support it.
Out of curiosity, what would those hidden costs be? not get enough Bitcoin business to justify the effort to support it.
Staff trained once, retains the knowledge. Wallets are free so as participation in the network. Legal help also is paid once.
What is that that I'm missing?
You are missing quite a few factors at play here
All in all, you are missing a good reality check if I can say so (no offense intended, just in case). Staff come and go, and still more so for big retailers. Therefore, you can't really expect to train them once. It is typically twice, thrice, and more times. The same is also true with respect to legal help as regulation, and Bitcoin regulation in particular, is rapidly changing, so it is not a "shoot and forget" thing either. In this way, without constant inflow of cryptobuyers, it may be not worth the deal after all. And maybe, you are missing something else here