£20m seems OK, I suppose.
He's 26 now, and despite being at Liverpool for three seasons he's only made about 15 league appearances, so it's unfair to label him as "non-scoring" - he's hardly played at all.
He's actually only had one proper season in the Premier league (for Burnley) and scored 11 goals - that's only one less than the likes of Lukaku, Firmino and Son managed last season - so there's some hope for Southampton there that he could do well enough if he stays fit.