oooh, another tough question.
to be honest i've not dived deeply into this aspect of parts.io yet.
partly that's because when I look at sliders like this for IGBTs for example:
...I just roll my eyes & say to myself "yeahwhatever". To get a meaningful range, I then have to slide the upper limit left to Min+1 several times to get to realistic price ranges - clearly the "remove outliers" feature isn't quite right here! THEN after writing this I thought "Why don't I just try sliding the upper-slider all the way left to Min - but it made no difference, whether I slid the upper-price-slider back to Min, or Min+1, I got the same results range back:
(If we were talking about FPGAs, for example, then such high prices might indeed be realistic, but for a 1000A/3300V big hairy IGBT that looks like it should be cavity-searched before it gets on a plane, $1000-5000 is simply a reflection of e14 & Mouser having it in their catalogue with no stock & adding a zero to the price. whether that's useful to anyone, well... shrugs).
Q1: So yeah, when outliers like that aren't filtered out (with the 'show outliers' button available), it's not misleading so much as it devalues the utility of the slider, & I haven't actually used it 'for real' yet.
Q2: Because of the vast variation in price vs. qty, and from my perspective having absolutely no idea where all your pricing data comes from (with Digi-Key/Mouser/e14/et.al. you know the price is based on their own stock, or at least history if out-of-stock), how accurate it is, how up-to-date/live it is, so my automatic M.O. is to 'herd the cats' by specifying a non-trivial order qty. that way I know I'm getting realistic prices & I don't have to mentally/visually filter out outliers, even if I know I'm only going to be ordering 10 for the first prototype @ several times the price.
But if I were working on a hobby project & know it's only ever gonna be a 1-off/etc, then I'd probably see it differently!
I think my point is that, with that top-level price slider, I don't know what it is I'm filtering out. By specifying an order-qty, I'm not filtering any parts out, I'm just filtering out 'noise'. I think they serve two different purposes?
So for that reason I find the price-breaks section of each item's detail page much more useful.
And now I just clicked on the price of an item in a long list, & saw the price-panel slide out (squeals in delight)
But then I clicked the 'Close>' button in the upper-right of the panel but it didn't close (Chrome/Mac).