I just purchased my first prosumer espresso machine (a used ISOMAC Rituale), using a Rocky grinder to share both coffee and espresso grinding duties. I want to purchase a dedicated espresso grinder that I can leave set up for espresso grinding. The used Mazzer Super Jolly's on eBay look like a good way to go, at worst I'd need to replace a set of burrs and maybe some assorted lids/hoppers etc. I must admit some envy for the MACAP MK7

although it's quite a bit more expensive than even a new Super Jolly--I've read the TGP and it's not clear to me that I would really be able to tell the difference between the two.
I've discounted the Mini because even comparing new prices for each it's not that much less than a Super Jolly and from what I can tell folks think the latter does a much better job. The MACAP M4 series seems to be in a similar situation, although the head to head comparisons are fewer.
I'd be interested in any experiences with purchasing a used grinder from eBay as well as other ideas.
Thanks in advance
Pat