They may look like the same machine but the actuality of using them is much different. The ability to synchronize labeling speed with the conveyor and many other settings mean you might be able to use the cheaper machine for simple straight round with a gap in the back but even that doesn't guarantee that your labels will work with your containers and that you have enough control over the internal operations to get a good consistent result. Another important factor is servicing, troubleshooting, computer settings and job memory, warranty, compatibility with the rest of your machine line, etc may not be available to you… 

Used Labeling Machines – Hidden Costs You Did Not Know About

From label-on.com:
https://label-on.com/used-labeling-machines-hidden-costs-you-did-not-know-about/