I have several Dell servers (desktop configuration) (T120 I think... used for backing up other computers and storing media. One is a Quad Xeon beast, used for serving up web sites.)
T120 was $200 brand new, but added several hard drives. The beast was $400 secondhand and required no upgrades.
Desktop is custom... Antec, Corsair PSU, Gigabyte, Phenom XII 940 Black Edition, ~8GB, some fancy mid-range video card from 2-3 years ago. 2 x Samsung SSD. Win 8.1
Probably spent too much overall. While I'd sell the previous parts when I'd upgrade, they cost something too :) Easily $1000+
Laptop was purchased with sign-on bonus for company that required BYOD - Dell Inspiron 17R 7720 Special Edition Core i7, 8GB, 256GB Samsung SSD. Win 8.1
Because bonus was taxed hard, I put about $700 of my money in.
Toy laptop was purchased before taking the big beast home after changing jobs. Dell Inspiron 3137 (11") with 8GB, Samsung SSD. Windows 10 Tech Preview.
Laptop plus upgrades was about $500.