Good choice!
If you take a look at this Metrics report, you'll see all eight 24-hour periods in which Namecoin hashrate exceeded Bitcoin.
https://metrics.namecoin.org/namecoin/period-timestamps-1-days/pool/charts/gt_parent.txtThe only consecutive 2-day period on that report is 12-13 November 2017. That was when BCH got into a hashwar with Bitcoin, with the purported goal of BCH being to prove that with more hashrate, it was the "real Bitcoin". Since Namecoin can use both Bitcoin and BCH as a parent chain, Namecoin wound up with a higher hashrate than either Bitcoin or BCH during those two days. When I tweeted about it, Samson Mow from Blockstream noticed my tweet and commented "Oh crap, now Namecoin is the real Bitcoin." So yeah that's what the shirt design is referencing -- a cool historical event in which Namecoin's ability to use multiple parent chains got demonstrated in practice.
The high price for the jackets is just because TeeSpring charges us a lot for those. That design is available on other products if you want something mildly cheaper. E.g.
https://namecoin.creator-spring.com/listing/real-light-1482?product=389That is not Namecoin, it's BitDNS, which wasn't even his idea. He just chimed in a few suggestions on how a BitDNS would work -- this was before the creation of Namecoin, which again, he had nothing to do with.
The Namecoin.org Team page credits Satoshi in the "Pre-Genesis Researchers" section, along with other people like Dan Kaminsky (who definitely would not be considered a Namecoin developer). That section is for people who did interesting research that laid the groundwork for Namecoin, but never worked on Namecoin itself.
https://www.namecoin.org/team/