Your local builder apparently either doesn't know where to buy or he wants to get paid big time. Lenovo says the K450e is $549 with a coupon code they provide. The extra components cost roughly $390, making a total of $939 plus the 8 Gb of RAM and the original power supply, together worth something closer to $50 than $100. Building a computer and installing the OS and drivers usually costs about $100 to $150 when you buy the components.
Out of curiosity I calculated a similar build at a major Finnish web and retail shop including building and OS installing. The total was roughly the same as your local builder gave, with the noticeable difference that we have 24% VAT included.
Building basically the same from scratch without any compromised brand stuff:
PCPartPicker part list:
http://pcpartpicker.com/p/nbh9Q7Price breakdown by merchant:
http://pcpartpicker.com/p/nbh9Q7/by_merchant/CPU: Intel Core i5-4460 3.2GHz Quad-Core Processor ($178.89 @ SuperBiiz)
Motherboard: Asus Z87-A (NFC Express Edition) ATX LGA1150 Motherboard ($54.99 @ Newegg)
Memory: G.Skill Ares Series 16GB (2 x 8GB) DDR3-1866 Memory ($120.75 @ OutletPC)
Storage: Seagate SV35.5 1TB 3.5" 7200RPM Internal Hard Drive ($58.11 @ NCIX US)
Video Card: EVGA GeForce GTX 960 2GB SuperSC ACX 2.0+ Video Card ($199.00 @ NCIX US)
Case: Thermaltake VL80001W2Z ATX Mid Tower Case ($21.99 @ Micro Center)
Power Supply: Corsair CX 750W 80+ Bronze Certified Semi-Modular ATX Power Supply ($69.99 @ Newegg)
Optical Drive: Samsung SH-224DB/BEBE DVD/CD Writer ($12.99 @ Newegg)
Optical Drive: Samsung SH-224DB/BEBE DVD/CD Writer ($12.99 @ Newegg)
Operating System: Microsoft Windows 7 Professional SP1 (OEM) (64-bit) ($133.79 @ OutletPC)
Keyboard: Logitech K120 Wired Standard Keyboard ($6.99 @ NCIX US)
Mouse: Microsoft JUD-00001 Wired Optical Mouse ($5.99 @ NCIX US)
Total: $876.47Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2015-04-15 15:14 EDT-0400