Let me ask you: Do you think that $1100 spent on an ebay package is a bargain versus $1575 from a company that does this as its main business and has been around a long time (i.e. DMM-tech https://store.dmm-tech.com/products/...c-servo-system ) and can and does provide support? (see other builds on here that have used these DMM systems)
I'm not going to get into the whole debate of what size motors is right and simply spout my opinion on a few other points.
Just think about finding compatible parts in the future - where are you going to find them - ebay again? good luck with that. So yeah, people can buy it and it can work, but if this is a longer term investment then ebay shouldn't be the source for this sort of part. Think about down time - how long are you going to be willing to wait to get your machine back up and running in the event something breaks (can break due to outside influence too - i.e. you drop something on a critical bit or send it past a limit by accident).
Also - something not always considered (just like with 3D printers) is safety. And there are a couple of areas of safety that should be thought of. First is electrical - ebay one is taking in high voltage AC (220V) - I see no safety certifications listed, not even CE which is completely self declared on most items like this (no 3rd party auditing to make sure you're doing things right). Are you willing to turn your machine into a giant electrocution hazard? (The system I linked to above uses a reputable name brand PS to convert AC to 48DC - a relatively safe voltage).
Next is the drives themselves - if they run away that's alot of power - people forget how much 750W is (basically 1 HP) - that can do a lot of damage, to your machine or you. How much do you trust these drives to behave properly?
But at the end of the day its your choice.
That's my opinion, worth what you paid for it

Mike