That's not exactly how it works.
For example, in this scenario with 0% hit and 0% exp, you end up with a chance to land a hit on a target of 71.5%. This means for every percentage of crit that you get, your actual crit % only goes up by .715% (1%*0.715).
Once your crit % exceeds 1/2 of your chance to land a hit on the target (71.5/2 = 35.75), you still continue to gain only .715% crit for each percentage added. However Expertise increases your existing crit % by 2% of your current crit % (on your character sheet). Thus at say 36% crit, you will gain .72% crit for each percentage increase of exp, as opposed to .715% for each percentage increase of exp.
This is for specials only. Whites continue to function normally and increase 1% for each 1% increase in crit. This means that since this concept is dependent on fluid values of Crit, Hit, and Expertise, there's no hard and fast number at which Expertise automatically becomes better than Crit. However it does happen sometime between 346 and 359 level gear, and will only continue to be that way as your Agility and Crit increase since there are practically no Expertise/Mastery pieces available to use.