In my time of working with JVDD TT's, I have taken Barium Ferrite and other Coatings that are an equivalent, becoming damaged as a serious consideration. As said, I have bought into having spare Platters to be available where possible.
Note: Platters show occasionally not monthly, maybe yearly if searches are maintained, but not for Sony Models I own.
The SP10 MkII Platter purchases are nothing to do with Peripheral Magnet Coatings, most bought are probably due to me being a hoarder, and having friends with their own designs for the MkII Platter hence the gifting of platters.
If I knew what I did today, I would own Yamaha and Micro Seiki over Sony and Denon as a multiple unit purchase, even though finding the cheaper sale models will have been over a longer period of purchasing. Reason being each are not using a Platter with a Periphery Magnet and each have models with the Electronics that are Off Board from the TT itself. These base designs will prove to be very easy to create the Kaneta Design, incorporating a Resin Impregnated Densified Wood Chassis/Plinth.
Hind Sight is always a good manager, but after having heard the Kaneta Version of the SP10 MkII and getting the core instinct the design is eking more than is already offered from a modified MkII. Stimulates the idea that a TT that is able to be produced as a Kaneta Design using Resin Impregnated Densified Wood Chassis/Plinth, is to be easily discovered as an improvement over the original design for the TT. Add to this other Treatments for the Mechanical Interfaces to add modern materials and remove the metal on metal contact that does occur and the possibilities become a whole new area of interest.
The SR 510 is also suitable for redesign for the Platter and is to be investigated to be used as a Kaneta Design, a Bearing Housing / Stator Bowl and with Electrical Lead Outs is purchased and to be learnt if the already produced electronics are able to create Spindle Rotation, Speed Control will be the challenge for this design change..
With what I know about Platter availability for certain Sony Models, and the cost I have seen models command, the idea that one minor damage puts the TT out of service is not a good condition to have running parallel with a very expensive purchase.
Does a Vendor actually inform that the Magnetic Coating in intact and no evidence of a damage to the coating is able to be seen???
If we were talking near $500ish, I would not say too much, one pays their monies and takes their chance. The TT is not too different from a sacrificial Cart', being after 'X' amount of hours in service it is spent.
The OP is into going up to $5K without an arm, I am not directing the OP towards any TT, that can have a really short lifespan due to being obsolete as a model and not known to have support readily available to correct a Barium Ferrite Damage.
If different is known to my experience of investigating Periphery Magnet Damage Repairs, I am all ears to learn what is known
As for the statement " not known to have support to correct a Barium Ferrite Damage.
I have too many years of looking for the fix, which has never been found.
I once found a TT which had a Platter Fixed that had a magnetic sensor design, where disc magnets were used as an alternative, the TT is not remembered as my PC crashed and the Bookmark went down the swanny.
A repair has never been discovered by myself that was a duplicate of the one lost or any other methodology as the repair.
There is the odd report seen where a TT owner is to claim they are able to use a TT with a Periphery Magnet Coating Damage, but these are very uncommon as report.
After doing many searches in many Countries, what is known and seen in a fair amount of forums, is that Magnetic Coated Periphery Rims on TT Platters get damaged from simple user mistakes, no different on simplicity to the simple user mistake made that trashes a Cart'.
Magnetic Coated Peripherals are Very Very Fragile - Non Repairable? - Spare Parts are Very Very Rare!! - Found on Very Very Expensive TT Models!! - Act in Haste - Repent at Leisure - Learn to Enjoy what might become a TT Ornament .