When buying vintage online, how important are movement shots?

Can you say "Dealbreaker?"

Going to edit it now 😎

Movement shots are very important for understanding the condition and authenticity of the watch.

I have bought watches without them, but not expensive ones.

I personally shy away from Vintage watches as I don't know enough to not get burnt . I like them , I just don’t go there .

It's very important,but not quite a deal breaker. It depends also on the description and the sellers history. Not all sellers are watch people,and that may reflect in the price, and price is also what I consider, if no movement shot is included I won't go all in on a watch. A little recent example I bought a vintage watch,no movement shot and it was described as an automatic, now after a bit of research I couldn't find any other examples that were auto,so I made a lower offer that I would have made if it was an auto and the sale went through. Glad I did as it wasn't an auto but its a sweet watch runs for 31 hours on full wind and loses less than a minute over that time,which isn't bad for a 55 year old watch.

I do not usually buy vintage, but if I were, I would want to see under the hood to see what I am dealing with. Risk is too high already, but getting a frankenwatch, which many vintages pieces are at this point (mostly unintentionally) would be a risk too high.  

I would say it depends on how expensive the watch is.  I would use the back movement photo to decide if I would go see the watch in person and to buy it.  So more of a flight commitment shot than anything else.  Also most people don't take great photos of the watch generally so making the visit to see it in-person is always worth it, if within 10-15%  of the watch price relative to the flight cost.

I have purchased many vintage watches - the only ones I've regretted were those that did not have a movement shot.

My advice - no movement shot = avoid. 

Exception is if you know the dealer and the watch is a verified NOS reference. Then you may not want it opened to preserve its NOS status.

This. I am so much more laissez-faire when it comes to vintage, and I only really do vintage. 

However, I am pretty comfortable when I drop on a watch what I am likely to get. There are other things to spot without popping the back to avoid a dreaded pin-pallet or frankenstein monster. 

My main concern is whether the damn thing works, I don’t have time anymore for ones that need fixing, you either tick or you get tossed. Servicing is different, but I can deal with a fair amount of drift.