There is the most economic option out there which is the Oculus Go, but it comes with one caveat: support for the device is phasing out starting december. Not only for AltspaceVR, but for the whole OS / VR updates. So you could only use it for one HiveFest and after that it would rapidly become an obsolete device.
I understand 300 USD (min) or 349 EUR is still quite a steep price. But if you like the new tech / games / dimension in brings it can be much more than a one-day entry to HiveFest. I'm at least a fan of VR now.
Depending on consumer rights, you could maybe also try one and return it if you don't like it, not sure how that works in your area.
Alternatively: there are 2d apps for mac & windows available: https://hivefest.freshdesk.com/support/solutions/articles/80000109626-how-to-get-started-on-altspacevr