IMO there are two ways to look as these.
.From a purely monetary standpoint. In the long run it is impossible to benefit from extended warranties, the business providing them has to make more than they spend or they close.
.From a stress/hassle/peace of mind standpoint. If it provides you some 'peace of mind', reducing stresses in general then perhaps it's a net benefit to you.
I think whether you buy or not depends on the latter, is the peace of mind/reduced stress worth the cost. For me it is not, however I've been wrenching on vehicles all my life and capable of handling any issues myself.