If you constrain your search to the specific flights that you're looking at, it should take ITA only a few seconds for each search. So assuming that you're only interested in fewer than half a dozen different booking classes, this should only take a minute or two. If you have a browser that allows you to duplicate tabs, then one refinement is to search for one booking class, duplicate the tab, amend the search in the new tab, and so on. Then you'll have all the different prices side by side in adjacent tabs.