I regularly attend and participate in major IT shows as a vendor. Proposals to spend at such shows are coming across my desk all the time. From this base I can assure you that fees to give a keynote, be listed as a sponsor (especially alongside the like of Amex) and structure a panel session (even for an MWC sub group) will be orders of magnitude more than the costs of sharing the Seattle booth.
SYT Price at posting:
3.0¢ Sentiment: Hold Disclosure: Held