Forgive me if I get a bit complex here.

First, get a rough idea of what your points are worth to you. If your own best use for them is short domestic hops for which you'd have to pay high mileage prices, it could be under 1 cent. If you use them for low-mileage international biz and you would pay the full posted price for those tickets, it could be 5 cents or more. For most people, something in the 1.4-1.7 cent range is pretty valid (depending also on what airline they are on).

Now compare the cost of an award ticket to a paid ticket. The cost of an award ticket it:

• Value of the miles; plus
• Taxes and fees associated with the ticket; plus
• Value of the miles you won't get by taking a paid flight; plus
• Value to you in your time and effort of booking the award flight (which is almost always more difficult than a paid flight); plus
• Value, if any, of the elite qualifying miles you will forego; plus
• Value, if any, of any elite status perks you will forego by getting an award ticket (if you are elite and have some chance of getting upgraded anyway, a premium cabin award ticket is less advantageous); plus or minus
• Any change in the cancellability conditions of a ticket. For example, if you have to cancel a trip, it is very likely you'd rather pay a $150 fee and redeposit the miles vs. paying a $150 fee and getting a voucher for travel within a year. On the other hand, some Delta award tickets are completely nonrefundable within 72 hours, so you'd rather have a paid ticket in that instance.

Not all these situations apply to the OP, but I thought I would try to make the list comprehensive for other people's situations.