So we really did our research and we can't seem to find any clear statement on limits and pricing at all! We've developed a platform using the Python programming language and are currently using a Bitcoin Client library which doesn't seem to be very scalable.

What we're searching

- A Bitcoin wallet service (has the benefit of visual representation and easy withdrawals)
- Most preferably we want to own the private keys!
- That service should be quite popular (-> reliable)
- There should be no (or almost no) fees involved - the service should be free and involve no monthly costs
- We want to receive Bitcoins (which should trigger notifications) and send Bitcoins
- All this should happen "behind the scenes" on the backend - we don't want to include any checkout page provided by the service provider
- We might need to generate 1 million addresses for a single wallet and hold up to worth $1M USD in BTC (but we could regularly withdraw)
- We need to get notified about each change in the number of confirmations

So basically we need a functional wallet API (for use together with the Python language). Does any such service exist? What for example about Coinbase? They do offer something... but no one attempts to clarify what's possible and what isn't!

Thank you in advance.