They might only be speaking for an hour, but I can assure you that giving a talk worthy of that slot and money takes a lot more than a single hour to prepare, even for the most experienced public speakers. You may be able to get away with that once or twice, but it's unlikely you'd be invited back to speak for any paying slot after that.
By itself, conference speaking is not going to be a good source of income for anyone at any level of experience. When you factor in the preparation time, it's always going to come out to far less than you'd be able to charge for hourly contracting (or even salaried work). The value in speaking at conferences comes from the ability to use the platform to deliver a message and to build your reputation (yours and your company's).
