If it were only the monetary value of the land that was in issue, I would likely agree with you. However, the problem in this case is that the monarchy's power is only restrained by the other major Houses of Andor, and the power of those Houses is determined by their land. By taking this land from their owners and giving it to people of her choosing as bribes, she sets a precedent that allows the Crown to replace disagreeable nobles with others of its choosing.

Obviously Elayne can't do this freely yet. Her rule isn't secure enough, and she needs to be gradual about it. If she tried to do this with, say, Ellorien there'd be a civil war. However,the precedent is set so that in years to come, when her rule is stronger, she can move towards such methods.

As our protagonists, we generally sympathise with their frustrations when they attempt to get something done and are impeded by squabbling from, say, the Hall of the Tower. But it is important to keep in mind that checks to power exist because someone will eventually abuse their authority. Andor is a monarchy. The next ruler will likely have as her only qualifications being pulled out from between the Queen's legs, and not having a penis. Are those really enough qualifications to feel safe with the eradications of any counterweight to their power?