Here's what rhymes with inestimable.

Consider these alternatives

immeasurable / battle incomparable / comparable artifactual / factual undeserved / first belittle / little magnify / high ascribe / right probative / native irretrievable / feasible unparalleled / help pecuniary / very undoubted / doubted diminution / solution demean / mean infrequency / frequency unquestionable / questionable overestimate / late disparages / marriages saponification / education rateable / agreeable