Having just returned from a sort of extended writing conference--a 3-year MFA program--I agree. We need community and inspiration and the guidance of more experienced writers.
I intend to include the cost of conferences into my professional expenses budget in the future, along with the price of writing tools, books on craft, research-related travel, journal and contest submission fees, etc.
The main point I would add to your advice here is to take stock regularly of your needs. If there are gaps in your writing skills (e.g. character or place description, screenplays, tonal shifts in poetry), then a skill-focused workshop may address them. If what you need is help with contacts and marketing, then look for a conference where many agents and publishers will be in attendance, like AWP. If you need inspiration and time to concentrate, consider a writing retreat directed by a writer you admire.
I'll say it one more time: writers need community.