Having just looked I'll assume you are refering to the prices from Fastlane?
Looks like the catalog is incorrect with the price for the new pump!
List price is supposedly the usual non-discounted price, the "Price" is what they will sell it to you for.
The core is the additional charge you have to pay when you purchase most rebuilt parts, after replacing the failed part with the rebuilt you have to return the removed failed part to the place you purchased the rebuilt from and if the "Core" is usable/rebuildable you will be remitted the "Core" charge you made with the rebuild purchase.
It looks like you'll pay $270 + $190 for a total around $460for the rebuild and when they accept your failed "Core" you will get $190 refunded. Or maybe you can ship the "Core" in first to reduce the upfront costs, but with some mailorder houses you have to ship he core directly to the rebuilder and then you receive the credit voucher ?
No matter what it looks like you would be best to call them directly to find out! Good Luck!