Oh it's a priority for him alright! Whatever he might say about having faith in Giroud / Walcott / Welbeck / etc, the fact is he's gone after a striker every summer for the last 3 or 4 years. I suppose his personal valuations could be hindering some deals, but I suspect the explanation is a lot simpler than that: it's just a shitty time to be buying strikers right now. Not much on the market to begin with, loads of competition for whatever is there, and 90% of them probably won't solve any problem for us.
To be honest, I've never had any problem with Wenger's valuations - I think he's generally proved right on most of them. Where I have an issue with him is that he often seems to have no cheaper alternatives lined up - if he can't get his man, then he'd rather go into the season with a gaping hole in the squad than take a more pragmatic approach...