Author here - in my experience, industry trade shows are terrible money drains if you don't have PMF. They can be more expensive than many online ad campaigns! I had a client who spent Over $50K on going to one, with booth and everything - probably got around 50 leads and only a handful turned into customers.
A couple problems.
1. This is just terrible advice.
2. Not all marketing is flashing rectangles. E.g. industry trade shows.