What % of the retail price would you pay for a set without minifigs? Seems like most people want the minifigues and that adds value tothe set. I'm not sure how much to pay when I see lots on ebays that ddon't have minifigures. Are blocks readily available to buy?

This all depends on how exclusive/rare the minifigures are. If all the minifigures are rare/exclusive then I would take off a decent amount from the value. If they are common minifigures I would take off a small percentage. If you are looking to complete a set, I would look for how much the minifigures are goning for on eBay. That should give you a reasonable value of the minifigures, and then you can subtract that from the value of the set, and you would get the value of the set if there were no minifigures.