Closed loop steppers are just now becoming cheap enough to be worth thinking about. I've just started fitting them to machines but In truth they offer very little more than normal stepper (open loop) when sized and tuned correctly. The smaller ones do have the advantage of using 3phase motors which give smoother action than 2 phase but other than that there isn't any advantage in power terms.
The closed loop side isn't really anything to pay thru the nose for IMO because at best all it does is throw a fault if position is lost. Thou to be fair this is the same for servos which only close the loop between motor & drive rather than fully closing the loop back to control.

Servos however get there advantage from the smooth linear power and speed they provide but the same holds true that if pushed too hard or tuned to high they will still lose position and the only advantage then is the fact they fault the drive. However this does come with a cost, both in money and technical knowledge required. They don't tolerate any corner cutting in control system or sloppy ness in machine. This means often the cost doesn't stop at just buying the servos.
Standard steppers cannot do this but if sized correctly and tuned correctly they are very accurate and reliable. They don't match servos in performance but they do Match Closed loop steppers in every way. They are simple and reliable which is why they suit DIY perfectly.