At ~3600 BTC/day, the current price of ~$350 / BTC requires ~$1.3 million of new capital (money, energy for hashing, etc) to enter the system.
Your list of capital types should include products and services.
Every person who sells their productivity for Bitcoin and does not immediately spend what they earn is contributing to that ~$1.3 million/day requirement.
The concept I like to focus on is accumulation (of holding). Every bit of that new 25 BTC mined every 10 minutes has to find a home with someone willing to hold it. It doesn't really matter if that comes from miners holding it, investors buying it, or people trading goods or services and holding the coins they receive. In reality all of these play a role, and they all involve exchange of other resources for coins, but we can be sure that aggregate accumulation is ~$1.3m per day.
It is indeed helpful to price discovery and liquidity that this forces a constant market clearing process. It is also no surprise that the scam altcoin market has moved to ICOs and proof-of-stake which lack such a process.