Thanks for your question. Yes multiple goggles can be built. A player may use the x ray goggles immediately before deciding whether to sell sets. So it happens in turn order in conjunction with selling.
-Ben Rosset (designer)
Uuoooohh, it happens before deciding to sell or not. That wasn't clear to me. I was under the impression it happened after market prices are adjusted, but before anyone begins selling. Well then, yeah, multiple players can build it. Thanks!