Scrap,
Temp is only part of the picture. Enstrom's have been running the 360 Lycomings for years at very high manifold pressure and temps and many of those reach TBO.
Ours are pretty much the same in terms of metallurgy and design except they're lower compression and have an oil cooled exhaust valve. Older ones are narrow deck and newer are the wide deck as well.
I've worked on all kinds of a/c for over 17 years and I'll tell you the best way to get beyond TBO is to fly regularly and keep your oil clean.
Sure if you can keep the CHT's down that helps but cylinders usually get changed due to loss of compression and that is typically a ring issue. It usually comes from inactivity. They sit, they corrode, lose compression, get excessive blowby, contaminate the oil, temps go up, valves get sticky, etc, ect.
My cylinder guy tells me he loves the Lean of Peak guys. They keep him in business
Excessive temps will change the metal but it's typically the rings that get affected and they will soften and collapse but that is mostly related to improper mixture/leaning more so than higher power settings.
Not to say, other problems don't occur but they're not nearly as common as what I've mentioned above.
Price wise, I'll tell you what I have into my engine so far:
Cylinder overhaul with new bigger exhaust valves and new pistons and rings - $4000
NDI/dimensional inspection of internal parts, polishing crank, grinding cam and lifters - $1300
Case inspection, repair and line bore - $750
Bearing kit, gasket kit and misc hardware - anticipate around $1100
Magneto overhaul - $1100
Fuel Servo overhaul - worst case - $800
Flow divider overhaul - $200
Ignition leads - $750
Fuel pump overhaul - anticipate around $750
Mechanical fuel pump - $250
New injectors - anticipate around $320
New Skytech starter - Ebay $250
New lightweight alternator conversion - $750
Additional misc parts - $1500
Assembly - no cost as I will do it myself, otherwise will probably be around $2000-$2500
My cost: around $14,000
My cost with someone else assembling the engine $16,500 so the previous quote is not too far off. Keep in mine though that I'm not including removal and installation either.