A multi-guest call room built on an existing WebRTC SDK is genuinely achievable. Broadcasting that call live to a large audience simultaneously is real, separate streaming-protocol work.
Borderline
Effort: a weekendRunning cost: $15–$30/mo
Why CanICodeThis says Borderline
A call room with host and guest video tiles, built on an existing WebRTC SDK, is a bounded integration
Basic on-screen overlays (name, title, slides) are simple compositing on top of the video feed
Registration and attendee email reminders share this register's booking-system pattern
The parts that'll cause problems
Simultaneously broadcasting the composited call to a live audience via RTMP is real streaming-protocol infrastructure, not an extension of the call
Reliable delivery at scale to hundreds or thousands of viewers is a different problem than a private call between guests
Interactive features (live polls, Q&A) at scale need real-time infrastructure of their own
How I'd build this
frontend
Next.js
database
Supabase
email
Resend
hosting
Vercel
MVP scope
Registration page with email reminders
A host-plus-guest call room via an existing WebRTC SDK
Basic screen-share and name overlays
Postpone to v2
Live broadcast to a large audience via RTMP
Live polls and Q&A at scale
Automatic recording and replay
What it actually costs to build
AI agent — with a subscription (Claude Pro/Max, Cursor, etc.)
$0 marginal
AI agent — pay-per-use API, no subscription
$43–$86 one-time
Hosting, once it's running
$15–$30/mo
Domain name, if you want your own
~$12/yr
Existing tools solving a similar problem typically run $14.99–$25/mo — see how they compare below.
The build prompt
Build me a webinar registration and hosting tool: a registration page with email reminders, and a host-plus-guest call room using an existing WebRTC SDK with basic screen-share. Don't build custom RTMP broadcasting to a large audience for v1 — a small, private call room covers real webinar needs at modest scale.