As @snailboat comments, OP is mishearing you're better off... (contracted form of you are better off).
Note that the speaker happens to use present tense here. But he could just as naturally use future tense (so you will be better off) or conditional (so you would be better off). In rapid speech both of these may be indistinguishable from so you be better off - but since native speakers know perfectly well that neither this nor OP's version are valid, they simply don't hear it like that at all (it's not what they expect).
In none of these cases do the speakers themselves normally think they're "deleting" words. It's important to note that OP's speaker pronounces you with the neutral vowel yə. This is a clear indication that he's likely to enunciate unimportant/predictable speech elements very weakly - possibly so weakly that they "disappear" to a non-native speaker who doesn't know what to expect/assume.
The moral of this is you should be very careful of assuming an unusual grammatical form when you seem to hear it in speech. If you can't find any written examples showing that native speakers recognise the words as you think you're hearing them, you may have got it wrong.
OP's particular example would rarely if ever occur in print, but it's worth pointing out that my "rapid speech future tense" version often would. But in fact even that would never be intended to reflect a competent standard English speaker - it would normally be intended to convey that the speaker had a rustic/country dialect (or be in unrelated contexts such as "How will you be better off if you do that?").