Ahh gotcha. If you need event introspection, doing it in-house is extremely likely to be more expensive (and definitely time consuming) than offloading it.

For example: if you are sending serialized data on your bus - you will need to write something that will deserialize it before inserting it into your elastic search cluster - and now you're managing even more infra (message systems, decoders, document storage).

There is definitely a price attached to the luxury - but we're betting that it'll be significantly less than doing it yourself.