Well, with that tight of a budget the best option would be to find a sponsor tbh. Just contact local(!) hosting providers and ask if they could sponsor such ev

Well, with that tight of a budget the best option would be to find a sponsor tbh. Just contact local(!) hosting providers and ask if they could sponsor such events. This would mean advertisement for them (maybe even tax deductible depending on the legal status of your organisation) and free resources for you. I can't think of any kind of on-demand service that will handle 500-1000 concurrent users for 50 hours that's under 100 USD. AWS nano instances are 0.256 USD per user per 50 hours (e.g. your workshop scenario), but that's still above your budget even with 500 users. Basically you'd need to find an on-demand hyperscaler that offers instances with ~1GiB + 1vCPU for less than 0.004 USD/h (500 users) or 0.002 USD/h (1000 users). Working on providing a simplified local install method (e.g. a docker image or a VM image hosted somewhere cheap) is the only realistic way to stay within your budget.