Its not that hard
1) People want keep comparing this to the original $250 Mark 7 price wise but they shouldn't, it should be compared to Midas if anything- which was $300 when it shipped 15 months ago and sold out in days. Stealth also comes with a dynamic stand, which is worth a premium. Movie Promos and Exclusives have a higher price point- this is reality, they charge it because they can as demand will no doubt be higher for a rarer item and also because they have a smaller amount of product to sell to make a return.
2) Its not just a straight repaint, there was some reworking involved (not much, but still). This figure has a finally improved eye size on the face plate (ala the Workshop Accessories Set), and it also includes some clear plastic parts in the design. The paint app includes gloss and matte, there are also decals. A bit more involved than just painting an existing figure a different color.
3) Its closest cousins are Gunmetal and Secret Project. Figures that are either owned by people who bought them for retail when they had the chance or bought them for up to 5x the price later. Secret Project was $210 in 2011. I'll bet if you went to that thread now you'd find the exact same mewling about how dare they charge such a premium for a repaint, etc etc. The Special Edition War Machine cost $240 compared to the standard $180 version. Well now it costs twice that.
Like it or not, this can be a "blink and you miss" it hobby. Deciding you want something months or years later will more often than not cost you a whole bunch more money, and this hobby is full of ever more people that have first hand experience coming in late and are faced with the gigantic prices on older pieces and are probably quite determined to not to get burned again.
Its $340, and that is expensive. But if it is worth it to you, then you buy it. If it is not, shrug and move on. Being loud about I don't want this and you all need to hear it in a way that belittles your interest is no more constructive here than it is when the exact same sentiment is expressed about someone else favorite movies, tv shows, music, sports, or books.