I would think lead time. To get the quote from your hardware vendor, get the PO approved from finance, get the box built and shipped, getting it racked and stacked in DC. This whole sequence can easily take longer than a month.
You can rent a bare metal server from Codero and get it provisioned in about an hour. Prices from about $100 to $1000 a month. At the high end, you get roughly what Google is offering here.
I would think lead time. To get the quote from your hardware vendor, get the PO approved from finance, get the box built and shipped, getting it racked and stacked in DC. This whole sequence can easily take longer than a month.