Sure, if you really intend to make aliyah just for the free education, and then leave right afterward and never come back (and thus never do your army or national service), then there’s something dishonest about that. If you really never come back, then in your case, Israel has gained nothing (besides your consumer spending when you were there, I suppose.)
But in practice, I bet Israel would love it if a lot of people did that. The more Jews who are Israeli citizens, the better, since they can always come back. Someone who made aliyah only briefly is still much likely to stay forever, or to come back permanently one day, than someone who never did. For example, they know there’s a good chance that while you’re there, you’ll fall in love with an Israeli, get a good job offer, or get swept up in Israeli patriotism or whatever, and end up staying despite your initial plans.
Also, if you have an open mind, and think that you might stay in Israel long term, or might not, depending on how things go, then I wouldn’t see making aliyah as wrong or dishonest in the slightest (even if it’s motivated to a large extent by the lower tuition). Lots of olim come back. That’s normal nowadays, and a lot of them probably knew that if they couldn’t find a job or had other troubles they would end up going back.