Not much. But, based on the report they bought $200 worth of fireworks containing about three pounds of extractable powder, they overpaid. A Fagor 6-qt pressure cooker is about $70 (unless you have one of the females boost it). The detonation system was made from a model-car remote (probably plus a carefully broken Christmas tree bulb).
These were not neutron bombs.
According the AQ Chef, these were not even chemical bombs. He reserves the term "chemical" for high (or "military grade") explosives, such as TNT, C4, and RDX. Rather, these were "mechanical" explosions in his classification, resulting from the deflagration of an inflammable material within a confined space.
This is an overall badly written article....more like they wanted to get on the bandwagon rather than report anything of signifficance.