My opinions on grading is from outside of the video game sphere. IMO the only things worth grading are things that need to be preserved due to their rarity. In general, this is to mean things that are rare but have a low value do to there being a low or non-existant collector market for it. And I do mean actual rare items, rare due to time or circumstances not rare due to limited production. Also getting something graded for the lulz, an item that has no high value, not particularly sought after but you want to get it preserved.
The value is a good consideration since most grading companies will charge a fee based on the current market rate. So unless you are sitting on stacks of cash, there is little reason to get a high value item graded.
I only have 1 graded toy which I purchased after the fact. Worthy consideration as it is Antex Camaro from Argentina and it had cost $75 at the time. Finding any Antex toy from the 80s in good condition is rare enough especially outside of South America, so this certainly fits my criteria. Here is what it looks like:
https://shmax.com/product_details/2903/camaro_blueI have purchased graded sports cards, but will not spend more than $10 for one, and thus it has to be something I really want. As for items I have gotten graded myself there are only 4 things that I am aware of. Two were rookie hockey cards that I did at a discount. One was a mail-away exchange card and the other was from Upper Deck Black Diamond which is notorious for wear due to how it is printed. The first one I ever did was a lulz grade, an baseball card variation where the guy in the background is readjusting his cup which is this card:
https://www.tcdb.com/ViewCard.cfm/sid/132/cid/53396/1989-Score-595-Paul-GibsonThe only item I had graded for preservation was a tobacco "card" (triple-folder) I had bought at a rummage sale for $1. It took a few weeks to identify it, and it turned out to be from 1895. As of this time, it is only one of two that are known to exist. There are 2 known graded and there is no photos of it otherwise. This is an item that is extremely rare but has an unknown value because the market for it does not exist.