Adwords is pretty simple to use and you control the cost of your campaign by setting a 'bid' for your advert to appear along with a daily maximum you are willing to spend. Once that limit is reached your ad will not appear again that day, but it guarantees your monthly expenditure. For example, you could 'bid' 5p per ad and set the daily maximum of £2, so your total bill would never exceed £62 a month.
The secret with Adwords is to spend some time setting up the 'keywords' that will trigger your ad to appear. I found that it was better to have relatively few but well considered keywords. If you use too many you risk the ad appearing to someone who is not really looking for your products.
The other area where I had real success was advertising in the classified section of the hobby magazines. The word rates were modest and I used a 'Tiny URL' to reduce the cost of the ad and make it easy for potential customers to type in.
Good luck with your listings!