My best guess is that a part of it is replacing US (or in this case Israeli) devs with much cheaper Italian/European ones, earning ~a quarter of their US counterparts and working longer hours, as Bending Spoons has an extremely competitive hiring process, and is probably the highest paying tech company in Italy
They are also very good at pooling their infrastructure and software stack. This accounts for a significant portion of the costs.
Actually they're paying very competitive salaries. For example: https://jobs.bendingspoons.com/positions/67c6dc18c70c531d6db....