Because the other links have no stock I guess your question is directed at the Surrey Timbers boards. It works out at about £200 a cubic foot, so somewhere between the price you'd pay for Honduras Mahogany and Sonokeling Rosewood. That is a bit on the high side for a fairly middle of the road European timber, but on the other hand Olivewood is notoriously difficult to source in clean, decent sizes and these boards are very useable and, depending on the project you've got in mind, should offer a good yield with fairly low waste. I've seen these boards first hand and for Olivewood they're pretty good quality, it's normally shot through with shakes and knots so the yield is terrible.
If it's a special one-off small project I'd be inclined to bite the bullet and pay for a special timber, if it's a big, bread and butter project then timber pricing becomes more critical. The question really isn't how expensive is the wood, it's how important is the project and is this the very best wood for it?
Good luck.