Prices vary depending on what you want. If you're set on a Dremel (certainly the most famous brand), then your best bet would be find a retailer near you (Dremel has a locator on their website
http://www.dremel.com) and find out from them what's available.
But be aware that while Dremel has pretty much become a replacement name for a mini drill (in the same way that many people call vacuum cleaners 'Hoovers' no matter what their brand), there are other brands to consider.
I use a Como drill myself (not as well-known as Dremel, but a much longer established company), which cost about £40. Como sell direct from their website,
http://www.mfacomodrills.com.
Have a Google for things like 'mini drill' and see what comes up.