Amazon reviews are frequently misleading. These boards should cost more money. Part of it is artisanal, part of it is quality of materials, part of it is workmanship. Materials, Time, Labor.
Family has a woodworking/lumber background and been exposed to woods of varying quality. Boardsmiths quality is much higher. Candidly I don’t feel the same about Boos, though I don’t feel it’s complete **** either. But good North American hardwood costs money. Trees take a long time to grow, and we’ve had periods in our history where a lot of forest was cut down unsustainably. The region of Pennsylvania near my family homestead, which was pretty much deforested by the 20s, so much of the forest is new, smaller trees. Saplings tend not to have as much intense color and have more knots and such which are both structural and hardness issues. Once you harvest lumber, you need to dry it out for a few years before selling it. That also takes time, and could be an area where a cheap board cuts corners. This can damage the board long term, because you're going to have shrinkage and spillage occur if the wood hasn't set. In the case of the example it also appears they use smaller pieces of wood which has disadvantages for more opportunities for warpage.
Once you get away from the wood, it also matters how you construct the board and what machines you use. Good quality machines to plane, saw, and join cost a lot more money. However, they run at lower RPMs and are less likely to cause cosmetic defects like burn on the figure of the wood. There's also an element of precision. Its pretty simply to get two pieces where you can glue them together. It requires a lot more precision to get them to stay together without splitting for years. Multiply that by all the pieces in an end grain board. Lastly, with the upper echelon of end grain boards you're paying for pattern and figure in the board. Each piece is not only put together well but selected for aesthetic.
Personally I don't think there is a cheap end grain option, if you want to buy a board that looks great, performs well, and lasts. I think there are half decent mid price edge grain. I also wouldn't recommend walnut for bread knives. Its a softer wood. I wouldn't spend much if you're going to be taking what's essentially a saw to it.