Alternative phrase to "highly paid job"
Solution 1:
Basically yes, that phrase sounds fine, though I might hyphenate highly and paid:
You have a highly-paid job.
I might also paraphrase it to sounds slightly more natural (though this is subjective):
Wow, you're highly paid!
"High paid job" is grammatically incorrect because "highly" needs to be an adverb to modify the verb "paid".
Solution 2:
High can be an adverb (with comparative and superlative forms) as well as an adjective:
adv. higher, highest
At, in, or to a lofty position, level, or degree ... [flew high]
In an extravagant or luxurious way: made a fortune and lived high. [AHDEL]
In that it has the same form as the adjective, it is known as a flat adverb
Obviously, the related -ly form exists:
He was rated highly by the judges.
That being said, I really want to see the splitting off of degree-modifiers (such as the prototypical very as in very quickly, very bright) and other secondary modifiers (such as mystifyingly silent, obviously troubled, off-puttingly tedious, oppressively close, overweeningly devoted, painfully obvious / shy, perilously close - to name but a few) into a separate word-class. Admittedly, they are almost always isoformal with related adverbs, but their function is very different - in fact, very can't even modify a verb, except whimsically (How very dare you!)
Returning to the possibility of using 'high paid' rather than 'highly paid', it depends on whether high may be used as a degree modifier as well as an adverb. Apart from very, most secondary modifiers are of the -ly form. Well isn't of the -ly form, and is only used very informally as a degree modifier (He's well cheeky!) However, in a high-flying aeroplane, we see that it can, though it does require the hyphen here. On the other hand, a highly paid job or a highly-paid job would seem to sound more natural.