Hi! Augustin here, one of the presenters of the talk: Alex actually built a vapour phase soldering oven from scratch a few years ago! Indeed they are not exactly practical for series production, though they are amazing for small runs of very challenging to solder board though.

Main issues is solvent recovery: as another commenter pointed out, Galden is very expensive, and it is also extremely greenhouse inducing and we were not confident in our ability to recover it completely, especially at "scale" (100 boards per month or so).

In our case, we picked a hot-air convection oven, which, while not as good as VPS, is still a lot better than IR at not burning components. Our main challenge is always space, so we went for a production batch oven which already has more throughput than we need for us to get to profitability.

The plan is to upgrade to a long and big conveyor oven once we move to a bigger facility, these are quite cheap and they are compatible with a fully automated production line.

Bit pricier https://www.crowdsupply.com/pcb-arts/vapor-phase-one

The working fluid for that thing costs EUR205/liter. Ouch.