Should a speaker attend a conference where he/she is required to pay their own registration fee?
Most international conferences are paid for by the registration fees of the attendees.  The higher the ratio of attendees to speakers, the more registrations the conference can afford to comp (give for free).  When a large fraction of the attendees are also speakers, as is the case with a lot of peer-review-centric conferences, then it's often the case that only the keynote speakers have compensated registration and/or travel.  If the conference is close on its budget, even the organizers are expected to pay their own way and their own registration fees.  The smaller the conference, the more likely this is to be the case, but even very big ones often expect everybody but the keynote speakers to pay their own way.

In short: yes, this isn't unusual at all.