When comparing the cost of pumps you need to compare flow rate and head capabilities, but most importantly, figure out total operating costs not just the purchase price. In most cases, you will be money ahead, usually in the first 12 months, by purchasing an energy efficient model. Based on energy costs of $0.08/kw-hr, a pump will cost $5.84 per month to operate for every 100 watts of power it requires.
An example would be:
Pump A (low efficiency) has a purchase price of $233.00 and uses 750 watts. Total Year 1 cost = $233.00 + (12 months x $43.80/month) = $758.60
Pump B (high efficiency) has a purchase price of $430.00 and uses 180 watts. Total Year 1 cost = $430.00 + (12 months x $10.51/month) = $556.12
In this example, you are money ahead after only 6 months, even though the low efficiency model was $200.00 cheaper initially.