A good registration committee will help ensure a smooth opening flow for the conference. The speaker budget does not have to be very expensive, but needs to include keynote and workshop speakers. Try to know what the speaker sounds like if at all possible. Some look good in their brochures, but come across poorly. Know your audience.
Costs can include their speaking fees as well as transportation and hotel.
Speakers will have various AV needs which can add rapidly to the costs. To keep costs down, verify the speaker's needs and use the equipment again for the next speaker whenever possible. The equipment is generally paid for by the day, not by the hour. Use it wisely. Marketing Marketing can take various forms.