The way you put it, this capex thing though is sounding like just sacrificing cashflow for some accounting sophistry.
Surely the main benefit of reserved instances is lower TCO and if you can show you can afford AWS for 3 years a bank would surely loan you the money to pay upfront if you can save say 50% it is simply cheaper even with interest.
Again this goes back to flexibility. RIs necessarily take away from your flexibility. AWS and others try to grant you the flexibility anyway, by allowing you to shift RI credits between physical instances, but lower TCO is definitely not guaranteed. If you buy an RI for a server type you're not actually using, you're spending money on servers that's getting wasted compared to not actually buying the RI.
