Its not super-exciting, as you frequently want your sideboard interaction to be streamlined and efficient, particularly when combating problematic artifacts and enchantments
I dont see this pushing anything up a ton since all of the Nekusar cards already spiked
Demonlord Belzenloks ability is a weird Demonic Consultation-like ability, where you have to exile cards off the top of your library until you exile a nonland card
For example, even for the same Pikachu promo, the budget and number of candidates will change significantly between looking only at PSA 10 and including PSA 9 as a candidate. Deciding your tolerance line first reduces wasted comparisons
It wasnt that Splinter Twin decks disallowed interaction, but rather that they demanded a very specific vector of interaction, and they were the lucky recipient of all of the benefits of the threat-theory/answer-theory matrix in that conflict
Because of this, well-preserved examples of the card go for a premium usually high five figures or even six figures