I am looking for free Google shopping feed apps that can create 50000 products feed and auto updates. Secondly is there any way to create Google shopping feed collection or group wise through single app.
However, looking into your assortment and potential average basket sizes you may have, I'd suggest you to play this more seriously and make sure that you partner up with companies like Fast Simon or sth. - also available in the app store.
Also, I am part of Prisync - an automated repricing app for Shopify - and strongly believe that some competitive pricing optimization may do wonders for your Google Shopping campaigns.