Your pricing is off by a 2X - he said he's ok with infrequent access, 1 zone, which is $0.01/GB, or $100K/month.
If he rarely needs to read most of the data, he can cut the price by 1/10th by using deep archive, $0.00099 per GB, so $10K/month, or around $600K over 5 years, not including retrieval costs.