It doesn't have to be expensive but if he chooses to go without then it will cost him in the long run.
What you/he needs is another ear in the room. Someone to listen for pitch, (Fiddlers are excellent at this) trailing notes, phrasing and so on.
The accompaniment was fine and I have no doubt that he is quite capable of judging the artistic content all by himself.
If you weren't a guest, I'd be able to PM you with details but we're stuck with this forum for now.