This doesn't change the fact robots are a very good investment. Especially if you are a Fanatic Materialist empire, which is probably the strongest ethic in the first place (because tech snowballs so hard). The initial cost is steep, as you pointed out. But it is very efficient compared to other methods. It also affords your primary species traits like weak.
I now know robot is very good method. But it isn't for basic guide.
I am kinda new to Stellaris, finished three games so far. I learned economy in first two games but I got hit by economy problems when I learned hard the robot mechanics in the last game because there is not enough explanation in gmae. I found that robot is better to build in low habitability planets, but should not build in generatinng world until droid tech, and most importantly, I should not research synthe tech.
I don't bother OP's playstyle or opinion is different from me. But there isn't enough explanation and he is just saying robot is very good. I disagree. One should know exactly what robot is better than biological pop to use it properly in early game. Sure, in mid-late game, there is more than enough resources so it cant hurt, always good investment.