POE 2 trade website question

Recently got into trading through POE website. I keep seeing mythical and really good rares going for 1 exalt. I whisper the person in game and they say 150 exalt or 1 div. Any reason why people set price on site and then have it different when trying to trade? Are they just listing it low to get the initial whisper? Sorry if this is dumb just trying to figure it out. When I go to put items on the site I’m trying to navigate if the item is actually worth a lot and I could ask for more/better currency or if it really is worth only 1 exalt.