The 4460 has a turbo speed of 3.4ghz, the 4590 has a turbo speed of 3.7ghz. The average overclock of the 4690k is ~4.5ghz
You cannot compare the price of the i5 4690k directly with locked models because there are two major variables needed to take advantage of the 4690k's "extra performance."
1. A more expensive Z motherboard
2. An aftermarket cpu cooler.
Add those two things to the price tag and the 4690k's value plummets. In most cases, you'd spend almost $100 more to overclock at the minimum.
PCPartPicker part list:
http://pcpartpicker.com/p/gpbdMp
Price breakdown by merchant: http://pcpartpicker.com/p/gpbdMp/by_merchant/
CPU: Intel Core i5-4590 3.3GHz Quad-Core Processor ($184.88 @ OutletPC)
Motherboard: ASRock H97 Anniversary ATX LGA1150 Motherboard ($66.99 @ SuperBiiz)
Total: $251.87
vs
PCPartPicker part list:
http://pcpartpicker.com/p/kx2kzy
Price breakdown by merchant: http://pcpartpicker.com/p/kx2kzy/by_merchant/
CPU: Intel Core i5-4690K 3.5GHz Quad-Core Processor ($214.89 @ OutletPC)
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler ($25.98 @ OutletPC)
Motherboard: Asus Z97-E ATX LGA1150 Motherboard ($94.99 @ SuperBiiz)
Total: $335.86