The cost and value are intensely personal choices, and I apologize for not stipulating more clearly that this is my opinion or entirely from my perspective.

Compared to 3G devices, the Tab is actually quite cheap at $549 or even $599 off-contract. 3G seems to raise the price quite substantially, and this seems to be with all devices. The Streak costs the same amount, and many modern smartphones phones cost around the same as well. On contract (from an admittedly small sample), I've noticed that the price is again similar to smartphones in price -- hovering around $1200 with data.

Of course, WiFi devices are far more affordable starting at around $300-$400 for a comparable device. Again, it depends on what you value. If you only want WiFi, then the additional $150 is a less justifiable expense. If not, it may be well worth spending.

Is it expensive? It really depends on what you consider to be expensive. For me, it's a value, to others it's likely to be outrageously priced.