Disclaimer in that I am not in any way an expert on military procurement: it depends on what they buy.
There are three European planes that can do similar roles: the Typhoon (Anglo-German-Italian), the Rafale (French), and the Gripen (Swedish). According to this RUSI article, it looks like the Typhoon is probably actually more expensive per plane. The Typhoon was also, unlike the other two and the F-35, designed to be a pure air superiority fighter, so it's more of an F-22 competitor than an F-35 one. Probably not what Portugal is looking for. That RUSI article has the Rafale as being a bit more expensive than the F-35 and the Gripen being a bit cheaper than it. However, the source for the F-35's number is the flyaway cost for the Americans, who did ordered it in huge numbers and also did most (not all, but most) of the development and I would assume get a better deal than others. Further, it's in an article headlined "F-35’s price might rise, Lockheed warns". So I'm just going to hedge my bets and say:
- If they buy the Typhoon, definitely no, but the Typhoon probably isn't the right fit anyway
- If they buy the Rafale, somewhere around the same, and it'll still be extremely capable
- If they buy the Gripen, yes, and it'll still be very good but not quite individually capable as the other options
The funniest possible outcome of this would be Lockheed Martin starting up a Tesla competitor