The tag line is actually all of the variations: "I'm worth it", "You're worth it" "We're worth it" depending on the structure of the ad. It's also meant to be uplifting so that customers feel encouraged to take care of themselves. Yes, that can be perceived as going to the extreme end of that, but the message at face-value is meant to be that you shouldn't feel guilty for caring about yourself across the campaign.
värd for en gender nouns and värt for ett gender nouns. jag of course isn't a noun, it's a pronoun, but pronouns referring to people (in the singular) are treated as en nouns. The plural is värda for all genders and for pronouns too. So Hon är värd det 'She's worth it' but Vi är värda det 'We are worth it'.