I forgot to say this, but you said it. Fiber is cheaper than CAT6A, and labor is the expensive one. If you have conduits, you don't need much labor then. Ask an electrician or a buddy to help out for a hundred or two for an hour or two and you can do it yourself. It's not a big deal (IF YOU HAVE CONDUITS IN GOOD CONDITION / SHAPE).
At 10g, sfp+ switches are cheaper and more available than 10gbase-T switches. Fiber transceivers seem reasonable, but I could be off; I've only looked a little at fiber prices, I already have cat5 in the wall, so I'm on DAC for nearby stuff and twisted pair for other rooms for the forseable future. I don't really need 10G, but it provides a bit of fun.
Yes, I have 10g over cat5. I don't need it, but I have it.
Ethernet specs are for cabling in dense conduit. Most people don't have dense conduit in their house. Much cable tests better than the rating on the jacket.
I am using 10G over an ~15m 4 twisted pair phone cable (PTT, common in France even decades ago for ISDN, but no cat cable at all) and don't remember seeing a frame lost in quite some years.