Time to get in this transfer. 100m fee + 200m wages for 4 years should be doable for us. If Juventus can afford it, so we can. He will improve our attack considerably - especially if we plan to win an another UCL - and he will have commercial value. Yes, spending 300m for a 33-38 years old player is quite a lot, but at the end of the day is 60-70m for year, which is just 10% of our yearly revenue.
Sure, he might get injured and everything can go wrong. Or he might play as long as Giggs who even at 40 was still a very useful player (for example, he was our best player vs Madrid in that Old Trafford match). Ronaldo is in an even better physical condition, and he believes that he can play in a top level until 40.
I am all for getting him. Him, Sanchez and Lukaku would be a formidable attack, which will put us in competition for every trophy.