The price doesn't seem out of line, however, I would like to address a couple of other points. First off, platinum rings are quite lovely when they are polished. One of the inherent problems with platinum is that it tarnishes and scratchs easier than gold, however, it is much more durable. Also, it is necessary for a jeweler to polish it properly. The Tacori band/setting is quite complex with many small areas that will be difficult to keep shiny. I suggest you compromise with your fiance by having the band made in white gold, and the center stone setting in platinum. The center stone setting will be much more durable than gold if you have it made in platinum, thus requiring fewer trips to the jeweler to have the points secured.
Here's a link to examine the difference between durability and scratch resistance. By the way, my wedding band is solid platinum and very heavy. I have it polished every six months and it looks great! Good luck with your choice.
http://www.ganoksin.com/borisat/nena...durability.htm