Several metal parts to fabricate there. The large aluminum extrusion at the front is just a piece of a common extrusion widely available. But it looks like some other pieces are not so common. They would need to be cut or stamped from aluminum plate. Each one would also have a motor with a motor speed controller so it can be set for speed. I don't see any adjustment for tidal volume, but some air is better than none. PEEP (positive end expiratory pressure) is important for Covid-19 patients but I suppose they could rig something up with the exhaust connected to a water bottle.
Metal parts can be cut or stamped out within a few days, then very quickly. But you may need to get the aluminum plate shipped to the metal shop. The motor speed control could be designed in one day, but fabrication typically takes several days to get PC boards and get the assembler ramped up. The motor is a bit more difficult. I assume they used a standard off-the-shelf motor. That would have a supply chain and some in stock. They probably come in from China. Beyond existing inventory, it would take weeks to get more.
So yes, it can be made inexpensively, but not fast to delivery of more than a few thousand. Maybe a few hundred. But it also assumes hospitals have a lot of ambu bags, which they don't. This is more of an ambulance item, for getting people breathing after respiratory arrest. As soon as they get them to the hospital they go on a ventilator. They probably have a few on each floor of the hospital for arrests, some in the ER, and more in the ICU. But not one in every room of the hospital. I doubt they have a lot of extra sitting around unused.
On the other hand, there is a story about a family in India keeping their child bagged for years by taking shifts. But I assume he is brain dead: You don't need much brain to breath.
Bagging is difficult because the person squeezing the bag also has to keep the nose and mouth mask firmly on the patient. Otherwise you can paralyze the patient and put in an endotracheal tube. Where do they get all those ET tubes? Where do they get all the anesthesiologists to keep them paralyzed?