Affordable is a relative term and most people want you to contact before they break the bad news!
I HATE that! You do too.
Well, I reckon that it is only fair to charge for the amount of work involved. Most site requests tend to be 'flat' - they are static with links to other sites and just pages of text. What's more people expect you to provide said text. If that is what you do for me then I will provide an up and going site for about £100 for 5 pages. If you want me to pursue your suppliers, via email, about getting your URL onto their site I can do that for a little more. If you want a shopping cart then it needs configuring and stocking and if you want my help with stocking it I can help with that - for a little more. If you want 'forums' or galleries, I can do that but - you guessed it - it will cost more. None of it is silly money, so don't be afraid to drop me an email! For 5 hours a week ongoing support (averaged out over time) I would charge about £20 a week. That is less than minimum wage!
On Going Costs
The above costs do NOT include web space (hosting) or the URL both of which attract ongoing costs but can generally be around £30 per year. Any less and the restrictions placed make it a worthless proposition, but a site with shop, forums and galleries could be around £200 a year. The ongoing costs include non of my effort and if I am wanted to be involved in ensuring the site doesn't expire then add on £10-£20 per annum. Revisions to static pages would be about £20 per page per request. I do not currently provide hosting but source it from proper hosting companies under your name and add nothing to those costs.
I DID SAY AFFORDABLE! But non of these numbers are set in stone and don't be embarrassed if we talk and you decide it is too much, I will have enjoyed the chat and you will have done my ego some good.