Base your decision on knowledge!
You don't have to buy the lowest price, but it is useful to know the price ranges of pumps that you are considering.
The Internet and Google are your friends. Sites like this are your friend. But in the end you must apply your judgement and make the decision.
You can buy Goulds pumps at
http://www.wwpp.us/goulds/goulds-submersible-2-wire.shtml 10GS07 = $572 + shipping
The 3/4 HP Myers Predator 2ST72
http://www.wwpp.us/myers/predator-2-wire.shtml with about the same characteristics is about $470.
They may not be the lowest prices but you get some idea what a good pump should cost.
When comparing pumps you must look at the curve, not just the GPM number. For example, a Goulds 10GPM rated pump has virtually the same performance as many pumps that are called 12 GPM pumps by other manufacturers.
You must figure out how you are going to install the pump if you buy it on the internet.
You might be able to leverage your knowledge to get a better price from another supplier, but you must also be careful about having the $$ addes somewhere else that you can't compare. All vendors must make a profit.