I replaced all of the bulbs in my house when they were 2 for $6.99 and expect a break even period of 12 months. This deal is even better: 2 pack of 400lm bulbs for $3.49 from Feb 14-16, or $2.24 for a 600lm bulb.
LEDARE LED bulb E26 - IKEA
LEDARE LED bulb E26 - IKEA
400 Lumen E26/Medium socket. Not Dimmable if you're into that sort of thing.