For comparison, I just picked up a Ryzen R7 2700, 16GB of RGB DDR4-3600 (GSkill) RAM, an ASUS ROG STRIX B450-F ATX mobo, for $205, $115, and $110, so $430 + tax/ship for those, then you need an SSD (got some 1TB 660p NVMe SSDs coming in soon, $88 + tax/ship for those, "open-box"), so we're up to $513, without a case, PSU, or GPU, or OS. So $675 does seem like kind of deal for that one. (Granted, if you build it yourself, you may not save money, but you often end up with a more robust and upgradable rig for the future.)
I wonder about the GPU, because one of our members ordered and then cancelled an RX 580 4GB card for like $127, that turned out to be a re-labeled/flashed RX 570. (Sold by Dell, apparently?)