The blues have been changed so that every 10 levels, each set is progressively better than the previous one. It used to be that only the odd numbered sets got the HP bonus for the top and the SP bonus for the pants. For example, I used my 75 cleric set until I hit the 95 cleric set, because I didn't feel that the slight defense increase justified giving up the HP/SP of over 500 each. Now, the evens (45, 65, 85) will give the extra HP/SP benefit too, so you should sell when you can get the next set item. As for price, try a little higher price, say 600S, and if it doesn't sell fast enough, then you can drop your price. If someone needs it bad enough, they will buy it.
Note to you smartasses out there - yes, my cleric carries the 85 safe set to change into to give the bonus to the endure buff, I just never use the 85 set for battle purposes.
