According to Techreport, although Haswell offers more flexibility the form of additional base clock straps, access to those straps is disabled in non-K parts. This means that with Haswell, overclocking support is now almost entirely confined to K-series CPUs.
Chipzilla’s argument is that non-K chips are targeted at the business and consumer market overclocking is not generally performed. Buying a K-series Haswell processor will another $20-$30 over the equivalent standard model. The Core i7-4770K is priced $30 higher than the Core i7-4770, while the Core i5-4670K is $20 more than the Core i5-4670.