Yearly, depending on when they renew offers little value. For example, if they renewed like 2 days before you bought them, you'd practically have to host them for a year before you saw anything. Then, if they leave, you've hosted them all that time for nothing.
For monthly, I think the going rate is still 6 to 9 months of revenue. So, the clients would be worth 6 x $10, or 9 x $10. They may be willing to take a lower price for quicker sale.
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