During the endless Brexit debates in the UK prior to the referendum itself, IIRC the more credible analysis tended to have the EU27 combined losing more than the UK in absolute economic terms, maybe even twice as much, in the event of a no-deal Brexit.
The argument was made that the EU could afford to take that bigger hit anyway and was still in the stronger position in negotiations, because as you say even a somewhat greater cost would be distributed over many more people.
Then the counter-argument was that the distribution of any costs to the EU would be far from uniform. For example, one member state in the EU27 was all but guaranteed a catastrophic outcome if there is a no-deal Brexit: Ireland. This is part of the reason the NI border issue was such a sensitive topic during the negotiations. But more generally, some member states are much more dependent on the UK than others, or more dependent than others in some specific area(s). Another common examples is that the Mediterranean tourism destinations get a huge amount of revenue from the Brits each summer (under normal circumstances at least, maybe not so much this year) and in certain cases this represents a significant fraction of their entire national economy.
The EU and the Europhile leaders that most of the larger member states have had in recent times have been very good at showing a united front when it comes to Brexit, but as we've seen with other issues like the immigration/refugee situation and the pandemic, that solidarity can rapidly give way to realpolitik when times get tough. A lot of the EU27 member states are going to take a hit if we leave the transition period with no deal at the end of the year, and I wonder how well their faith in and support of the EU will hold up once real money and real jobs start being lost on both sides of the Channel.
At this point, I do not expect there to be a deal, at least not a comprehensive one that is useful for the long term, by the end of this year. It won't surprise me at all if the cracks start appearing on the EU side soon afterwards, though whether they will spread as quickly and as deeply as those likely to form concurrently in the UK is anyone's guess. It also won't surprise me at all if some important issues that are, in theory at least, EU competences start to get dealt with more directly by national governments looking to protect their own interests. Time will tell.