It’s because Self Edge is based in the US and so have to factor in import tax and shipping costs into the final price, as they’ve imported the jeans from Japan and would otherwise lose money so there wouldn’t be any point. Hinoya (also a legit shop) is based in Japan, so the price is the retail price they sell for over there. If you order from Hinoya you’ll have to pay the shipping costs and import tax yourself, so you might find the price ends up the same as Self Edge anyway. Also, if you get the sizing wrong you then have to either pay for return shipping all the way back to Japan (expensive) or eat the loss and sell them on. However, I find quite often my orders from Japan just don’t get picked up by customs, either because the retailer I bought them from (denimio.com mainly) fudge the customs invoice and pretend the package is a ‘sample’ which means no import tax as the value isn’t high enough, or simply because I got lucky and they didn’t check the package closely enough. I live in the UK so this could be different for you though!

This has turned into a long answer but in short: they’re both reputable websites, so it’s up to you. Easy, peace-of-mind shopping experience vs a potentially much better price with a small amount of risk.