Another of Gordon Brown's weird mispronunciations: he says "gross" to rhyme with "floss" or "dross". The word is in common usage, especially when taxes are being considered, so you wonder if he really does listen to what anyone says.
In fact all words in -oss have ɒs, i.e. the vowel of CLOTH or LOT, with this one exception. We have ɒ in boss, joss, loss, floss, gloss, moss, (a)cross, dross, albatross, toss. Only gross and prefixed engross have əʊ, the vowel of GOAT.
Unless you are Gordon Brown.
Note the inference that can be drawn if you produce a one-off spelling pronunciation: it means you don’t listen to what anyone says.
Words in -ost, though, are unpredictable in this respect. On the one hand we have cost, frost, lost with the CLOTH vowel, but on the other hand ghost, host, most, post with GOAT. Does hostage rhyme with postage? Or foster with poster? No.
It’s the same with -oth. CLOTH: cloth itself, and also Goth, moth; but GOAT: both, loth and, for most of us, sloth.
Not only EFL learners but native speakers too must learn the pronunciation of a word when they learn its written form. Otherwise people mock.