It was actually natural KB but it was heated when I had specifically asked the question and was told it was unheated (by two different people). When it arrived the cert clearly said heat treated. That affects the price and made the gem actually then quite expensive compared to other gemstones I was considering (not to mention the colour on this one didn't match their gorgeous photo AND it had a massive window). In the end I bought a bigger, certified as natural and unheated sapphire elsewhere for much less *cheesey grin*!
I don't recall the cert having a valuation on it. In fact I'm positive it didn't. It was a coloured gemstone report from the IGI (if I remember correctly).
The thing is that natural sapphires will always have variances in colour - you consider how much rough you'd have to have to cut all these stones to have the same colour. A good lapidarist will typically get about 30% yield from rough. Then add in that purple sapphires are indeed very very very difficult to come by and you've got an (almost) definitive answer that these are BE treated (which is why you get a uniform colour). Just to satisfy curiosity, do a search and look for Purple Sapphires - what you'll find are pink/purple, blue/purple, purple/red, purple/blue, purple/pink etc. To get a pure purple sapphire you really have to search long and hard. Then try to find another ................. you'll be searching for a very long time!