True Brian, thank you for reminding me how international this forum is!
What Epson actually do is have their Service/Repair co. send a quote with all the possible parts on there, plus the technician hourly rate etc. So everything from the head to capping stations/ cleaning assemblies, mainboard, etc. are all shipped to you, and what is needed is used. The rest is returned and not charged for. Sensible approach in one way, as all the parts are on hand for the call. So it most likely would be less than the $5000+ worth or parts and labor on the quote.
That said, the most expensive thing -the head- is invoiced at $3500, when Compass Micro sell them here in the USA for $2800. So you're clearly being gouged 'paying full list' on parts. On Alibaba the heads are under $2000. Hmm.
Anyways, what I am going to try first is soaking the head in ink cleaner overnight. These machines have a 'head maintenance' routine that parks it over to the far left and allows easy access to the underneath, so that's not hard to do. Likewise you can attend to cleaning the wipers and capping station on the other side.
If nothing works. well. Yes the Canon is a little slower, though the newer ones (Pro-6100, vs old iPF9400) are a lot faster, with bigger heads. And a new head is $445! & user replaceable!
Or... a new P20000 for that matter, I mean its just a few thousand more than a head swap, and you get a brand new warrantied machine (with option for extending) and a set of starter inks. That kind of makes more sense. Its just so retrograde to do this. Makes me mad at Epson for not considering the environmental cost of their approach to repairs and replacement parts.