-DIr is normally used for encyclopedic facts and strong assumptions. You can read more about it here: https://www.duolingo.com/comment/8649151
We accept it, but it sounds really artificial in most contexts and would almost never be used in spoken Turkish.
You could either say this exactly sentence or replace "çok" with "fazla" if you want to get the meaning of "too expensive."
I wrote, ' his television is very expensive' then checked the word clue and it said 'he has.' Being on a correct answer streak, I didnt want to take a chance and changed my answer to 'He has an expensive television ' and was promptly marked wrong, grrr Tool tip clue should be editted to his, her, it's. As duo does not accept he has, she has etc. And this happens throughout the course. Now after taking this misleading road for the umpteenth time, I realised that if 'var' is there in ithe sentence then I should translate to, he, she has otherwuse I shoukd go for his her and it's