Sounds like a terrible tradeoff, isn't it?
I also don't get your focus on education, this is Europe, not US where college costs 200.000EUR per person, the aggregate education costs don't even come close to tax breaks.
Living for locals getting expensive is because of higher paying jobs - whether or not it is the immigrants who are helping build those industries - no? What is stopping local realtors building more affordable housing for more people? Imo. these immigrants are just accelerating the process of those industries being built.
And I meant more than just taxes. Expat friends of mine are spending 50-60% of their income in the local economy itself. So even if they are getting taxed at 20-30% lower rate for the first 5 years, they probably spent a lot more than the missing 20-30% taxes to gain the skills needed to move there. Do keep in mind that the employers won't be hiring them and moving them from elsewhere if they are not generating more revenue than they are taking in.
So the expats spend their home country resources for 20-25 years to get educated and be qualified enough to leave it and contribute to a different country's economy, taxes. Now the host country didn't spend any of it's resources in it's education, nor will it contribute to their healthcare - which typically becomes a burden only once they are older, by when they'd have left the country. Still seems like a net positive to me. Just can't put a number on it though. (wrt the 30% tax benefit).