Your client could auto-zap it when replying if you have a built in ecash wallet or NWC set up. keychat (npub1h0u…rwx8) charges you 1 sat to send a DM and it seems to work great. I’ve only sent a couple messages though.
If you only read from paid relays, you’ll miss out on all the notes from people that can’t afford to pay for the relay. Paying 1 sat to post a reply is much more manageable than paying 50k sats upfront for a relay.