Nowadays, it is possible to get almost anyone in front of the microphone if you pay them – but does it make sense? Keynote speakers and celebrities are popular choices, but what if their fame is rather limited? Or opinions about them are divided? In addition to their fees, celebrity speakers frequently also charge for extras such as travel expenses. Security issues also feature, particularly with regard to prominent business people and politicians.
They are not the only option. The key issue is, what do you want your conference or convention to achieve? Is it for training or motivation? Is it an incentive or a promotion? Is it a forum for academic debate or for attracting the media? Much less expensive solutions may be more practical.
Many speakers are company employees and are not permitted to accept a fee at all. Others are from academia and are glad of a platform for presenting the results of their research, and there are also professional speakers at the beginning of their careers who are keen to speak for a relatively low fee. In any case, you should form you own impression in advance – and don't be afraid to negotiate. The same applies to moderators, who often have to intervene and 'save' a situation.
Tip: Make it a contractual requirement to receive a preliminary digital recording of the presentation so that it can be checked and loaded into the AV system and/or incorporated into official documents.