I guess the real question is how good do you think Jimmy Butler is (and Faf has done a nice job providing statistics to back up his opinion)? He is better than Avery, but Avery also fits his NBA role so nicely that merely comparing the two doesn't really do him justice. Jimmy Butler is an all-star and can likely be a 2nd/3rd option on a contending team, but I don't put him in that upper-echelon of above average all-star/superstar. Again, that is just my opinion.
My take has always been Avery, Young/RJ, #3, #23, and however many 2nds they wanted. I am fine with this deal not getting done - unless, of course, it's the reason we don't get Durant (I don't think that's the case). Crowder was completely off the table for me.