There have been numerous problems with the organization of booths in the past. This document aims to shed some light upon the issue.
First of all, the Debian Project does not have any money to spend on exhibitions, especially not on returnables (such as floor space, carpets, tables etc.). As a result the project needs to get the entire booth sponsored by the organizers and not just floor space in order to run a proper and well staffed booth.
Secondly, everything that is shown on a Debian booth during an exhibition is loaned from individuals or companies who provide a means of support to us. All equipment is maintained by Debian people who are interested in running that booth. All expenses, be it lodging or travelling, are normally paid by these individuals out of their own pocket. All other expenses that make the booth look interesting (i.e. banners, posters, t-shirts etc.) are also paid by individuals.
This means that when providing only floor space for a booth, the booth would look very poor, since no electricity would mean that computers won't be able to display anything (since electricity is needed to power the machines and monitors), or only laptops could be used, but they can store power for no longer than four hours. Additionally, it also means that people, who would staff the booth, will actually have to sit on the naked floor if nobody provides tables, chairs and a carpet.
In short, such a booth would look very poor. It is quite questionable whether this would demonstrate the high level of an exhibition, poor project or display that the organizers don't have money or don't want to spend money on free software projects.
After all, such free software projects create the products what the organizers get paid for. Without all those projects that provide this wonderful free software, there won't be conferences covering this very software. There also won't be many companies that base their business on this type of software. Taking this into account, where is the problem for conference organizers to provide a fully fledged booth for these projects? How much is $500 to spend for one booth for a company that take in an entrance fee for a single person which is more than this?