A virtual conference organised by a non-academic organisation such as this carries several costs. A non-exhaustive list of these costs includes: administrative staff and sub-contractor salaries, national insurance; website hosting, design, maintenance and updating; accounts and taxes; business insurance; software licences; equipment, and office space. These are fixed costs and are not reduced whether an event is held virtually or in-person. Furthermore, live-streaming of in-person sessions is expensive and incurs additional costs.
There are costs even for the conferences organised by academic institutions and societies; however, these costs are generally absorbed by the institutional infrastructure (IT support, computers, software licences, administrators, office space, etc.), academic salaries and grants from funding bodies. We do not have access to any such infrastructure free of cost or funding.