Surge protectors--how many $ make sense?

I use a whole house type II (at the main service panel) from Siemens plus on the main system, a surge board in the iso transformer that protects the outputs- 4 gauge to a sub panel that feeds 10 gauge dedicated lines. For most appliances, computers and my vintage system, I use point of use surge protectors. I keep the antique Quad Loudspeakers in the vintage system on constant charge using a Zero Surge.

"Whole house" may not be sufficient (some surges are within the household system and the "whole house" will not address these); in the realm of "point of use," a lot of the conditioner/surge protectors have a sound. That’s where you have to experiment through try before you buy or buy with the right to return with minimal penalty. The Siemens FS 140 is overbuilt, but still uses MOVs and has gone up in price; I used an Eaton before that. There is an "audiophile" whole house by Environmental Potentials that is now about twice the price of the Siemens, have not tried that unit. There are also more industrial/commercial units that can be even more spendy.

My go-to on electrical systems is @Jea48. Others here are also knowledgeable.

I forgot to mention that on new construction and work done on existing systems, a whole house surge protector is now required as I understand it. 

Yep, @erik_squires and there is a 2023 edition with further "clarification" on the subject but it depends, as you said, on the locality. This link purports to identify state by state adoption of the NEC and which version applies: https://www.mikeholt.com/necadoptionlist.php#:~:text=The%20NEC%20is%20adopted%20and%20enforced%20at%20the%20local%20level. 

I don't know (this is where @Jea48 comes in) whether, if the state is stuck on an older version of the Code, a county or city within it can demand that the newer Code edition be enforced within its jurisdiction.