I wonder why they charge a minimum of $0.90 per node-hour when they offer VMs for as little as $0.008/hr. This is hugely useful even for single-person startups, so why charge a minimum of ~$8,000 per year?
Companies with more data than can fit in a single-instance RDBMS system (like >3TB of hot data, more throughput than a single node can handle) but still seeking transactional consistency are a clear use case. Single-person startups could definitely benefit, but it's a less-likely scenario that they would require the level of coverage Spanner provides.