of computer-literacy can design a website, but there's a difference between a website that's designed for a bit of fun and one that has to earn its living as a shop window for a business.
The figure you have been quoted is perfectly reasonable for an average starter site, but to be honest it's difficult to be more helpful without knowing a lot more about what's included in that figure. Only you can judge whether the expenditure is likely to be warranted, and don't forget that the design fee isn't the end of it - you'll have to register a domain name, and pay for a hosting package. Those items aren'tgoing to break the bank, but you'll want to update the site at regular intervals, and the cost can start adding up.
If you have the enthusiasm, the time, and a bit of money for some software you may find site design a rewarding experience, but there's a learning curve associated with even the simplest of sites.
Mull it over, and if you want any further help or advice just ask.