The entirety of all the podcasts on iTunes/Apple Podcasts RSS feeds downloaded is around 200-250GB across the 2.5M+ pods. Hosting the RSS feed should be an easy task. Add in caching via ETag and server-side (host the feed as a static file, only re-render when user updates something), and your server load goes down drastically.

It gets a bit complex if your hosting company supports dynamic audio/ad insertion depending on how you accomplish that, but as far as retrieving the RSS XML feed, that has no impact.