It's extremely fair to compare depreciation against MSRP. What's not fair is to say that they were being "sold new at massive discounts" when in reality it's an asterisk-ridden rebate process that applied to one model year under specific circumstances. That article was spam when it was written, can you provide a first party source for these massive discounts?

Depreciation is measured against the price someone actually paid.

The MSRP doesn’t matter. The S stands for suggested.