Is IPMAT of the same difficulty level as the sample paper given on IIM Indore's website?

First of all the paper available on IIM Indore’s site is not a sample paper. It comprises some difficult questions from the last IPMAT paper. So yes, the questions asked are of the same difficulty level. However, some questions may be easier as the available sample paper covers the most difficult questions.

The Aptitude Test is especially challenging for the students from Commerce and Humanities stream. The Mathematical part is very difficult and those who did not opt for Maths after High School will have to prepare extra hard. To have an upper hand one needs to focus on higher Mathematics as well.

I have seen instances where students cleared Symbiosis and NM entrances but lost IPMAT as they couldn't clear the AT cutoff. 

Don’t forget to prepare for the other sections as well i.e., Verbal Ability, Data Interpretation, and Logical Reasoning. They carry equal importance.