So as mentioned nobody from Apple will reply, but here is a second opinion on the two different repair costs mentioned.
Generally speaking Apple does not repair out of warranty iPhones, but replaces them with refurbished units for a set cost, which I believe is the 155 BPDs which you were quoted in person. This would replace the whole iPhone.
Apple does have an iPhone out-of-warranty battery replacement program as mentioned here:
http://www.apple.com/uk/support/iphone/service/battery/
One of the first things mentioned here is that "Your iPhone is not eligible for Battery Replacement Service if the product has been damaged, for example, as result of an accident, liquid contact, disassembly, unauthorized service or unauthorized modifications, or if the product is not operating correctly as a result of a component failure. Please review Apple's Repair Terms and Conditions for further details."
If you went in person maybe the person in the Apple Store noticed some sort of damage or a tripped liquid sensor which he/she felt would make the iPhone ineligible for the battery replacement program. Or maybe since the original iPhone's battery is soldered in place it is not eligible, I really don't know.
You could always print off the iPhone out-of-warranty battery replacement program webpage and take that in with you incase the Apple employee was not aware of the program. If your iPhone is not eligible then you could always get a better explanation as to why as well while you are there.