I have no reason to believe that they are. It seems to me that the burden of proof is on those who are making the accusation that Google will be collecting this data. I am suggesting that we have no idea, and in fact I think it would be pretty shocking if Google were actually to collect that data. Hence my accusation of FUD. But if you have some sort of evidence please share it.
Here's a thought experiment: my Android phone has a camera in it. Do you also believe that Google is collecting every picture I take without my permission?
Technically neither does the transaction data. I mean, there's no technical requirement that transaction data needs to be stored on a central Google server.
They could have made some arbitrary statement like "by using the camera app you give us access to all of the pictures you ever take, so that we can back them up for you."
Maybe I'm misunderstanding google wallet, but isn't this exactly the kind of data that you would expect for it to collect? I'm not too shocked when my credit card statement has a list of merchants, addresses and times of purchases, nor when amazon (and newegg, and paypal, and...) has a list of items and dates purchased, which in turn influence the items they recommend to me for future purposes.
On the other hand, if you don't feel comfortable with google being the clearinghouse for the information...super? Use something else (and spur competition!). The OP's statement seems as monumental as which brand of credit card company he uses (and somewhat willfully blind in light of the information they can and do collect...much more than appears on our credit card statements).