I'll try a brief answer first and THEN look at the data sheet and costing :-)
It is most likely very low power and/or can run from low voltage. Low speed assists low dynamic power reduction and the lack of need to support high power and speeds allows lower power to be targeted.
You may also value the low EMI aspects.
OK - lets look at the data sheet ...
Phew! Got it right :-)
The first few paragraphs of the data sheet tell the tale. Very strong emphasis on low power for long life in battery applications and low voltage operation to suit battery power.
Micropower, Rail-to-Rail Input and Output Operational Amplifier.
The LPV511 is a micropower operational amplifier that operates from a voltage supply range as wide as 2.7V to 12V with
guaranteed specifications at 3V, 5V and 12V.
exhibits an excellent speed to power ratio, drawing only 880
nA of supply current with a bandwidth of 27 kHz.
These specifications make the LPV511 an ideal choice for battery powered systems that require long life through low supply current,
such as instrumentation, sensor conditioning and battery current monitoring.
The LPV511 has an input range that includes both supply rails
for ground and high side battery sensing applications.
LPV511 output swings within 100 mV of either rail to maximize
the signal's dynamic range in low supply applications.
In addition, the output is capable of sourcing 650 µA of current
when powered by a 12V battery.
For perspective - 880 nA or 0.88 uA is somewhat less than a gnats breath.
880 nA for one year is 880 x 8765 / 1,000,000 mA/nA ~= 8 mAh/year.
Operated from 3 AA Alkalines of about 2500 mAh capacity and 1V/cell end point and with no shelf life consideration, you could run one of these for about 300 years. Or, in a real world situation with a say 5 year shelf life and half capacity taken by battery degradation and a 2500 mAh initial capacity, this is about
8 mAh/year x 5 years / (2500 x 50%)
= ~ 3% of the available battery capacity.
ie you could run 30 of these for 5 years from 3 good quality AA Alkaline cells or have much other circuitry and a few of these with a 5 year life. Or use a 3V nominal Li coin cell and a few others things and get good lifetimes.