I haven't changed any dials myself, but as far as I remember those members who have didn't get the original dial back. My guess it is to prevent access of real parts to the replica industry.

Correct, Breitling keeps the old dial. The $800 quote is also likely low, because Breitling tends to also insist on a full service. There is some recent evidence that it's getting cheaper on discontinued models, but not current ones.

Additionally, if you buy a dial from eBay and have a local watchmaker change it Breitling will have no record of it and may well change it back (at your expense) during servicing. I also don't believe that Breitling will change a dial to a user supplied dial.

I asked them about this with the Chronomat and got this reply

Me I also bought this very early Chronomat its reference no is B13047 but I cannot find a serial number for it.Its face is slightly pitted and I have bought a brand new face for it and intend to send it in with the face for you to service it and change faces would this be ok?

BUK With regards to the Chronomat, you are of course very welcome to send it in. We would usually only fit dials supplied by ourselves however if you would like to send in the watch and the dial that you have, we can have a look at it for you. We would need to ensure that it is genuine, correct for the model that you have and not damaged in any way. It may be that we generate an estimate for the whole repair.

Me The only reason I bought the dial for chronomat was I didn’t think you would have any that old left.

BUK We are still able to get the dials for the B13047, however as previously mentioned you are very welcome to send your dial into us and we will look at fitting it for you.

This is taken from the email I recived so I guess they may fit the dial for you if it were correct for that model and all else was above board.