There are certainly cheaper motherboards. I'm more than happy with my ASRock Z77 Extreme4.
Including EVERYTHING in my rig, cables and misc supplies in all, I spent just under $1,800.
CPU: it-3570k ($189 at MicroCenter)
CPU Cooler: CM Hyper 212 EVO ($29.99)
Motherboard: ASRock Z77 Extreme4: ($94.99, bundled discount with processor at MicroCenter)
Memory: G.Skill Ripjaws X 2x4GB ($44.99)
Storage: 2x WD Velociraptor 300GB in RAID0 ($69.99 each, got both on sale
)
Storage: 32GB SanDisk ReadyCache SSD ($49.99, very effective)
Video Cards: 2x Gigabyte Radeon HD 7870 ($259.99 each, one included $110 in free games)
Case: Thermaltake MSI Commander Epic ($49.99)
PSU: OCZ Fatal1ty 750w ($79.99)
Optical Drive: LG Blu-ray Combo Drive Model UH12NS29 ($39.99, on sale on Newegg)
Operating System: Windows 8 Pro Upgrade ($66.99, used an old copy of Windows Vista)
Total: $1,305.88
This doesn't include my monitor, keyboard, mouse, speakers, 8 120mm fans, 3 40mm fans, fan speed controller, internal cables (SATA, fan splitters, etc.), 3.5" card reader, and 5.25" HDD cooler mount (for 40mm fans).
I have Razer peripherals, which added a big chunk onto the cost. $50 speakers, $150 monitor, and loads of small internal items. She's quiet, cool, and fast.