We have a new site www.g-lish.org where you can read all articles from This is Ghana in a much more organised fashion. Read Cost of living and travel in numbers there.
The exchange rate is approximately 1 Ghana Cedi = US$0.55. 100 Pesewas = 1 Ghana Cedi. (Like cents to the dollar...took me a while to work that one out.) US$1 = about 1.15-20 Cedis. It is fluctuating a lot at the moment so double check when you have to do the sums
375 ml bottle of Coke/Fanta/Sprite 40-45 pesewas
500 ml sachet of water 5 pesewas
500 ml bottle of water 50 pesewas
Bottle of Star or other local beers 1-1.20 Cedis
bowl of rice, egg, beans and stew on the street: 50 pesewas-1 Cedi
1 Grilled plantain on street 20 pesewas
1 bowl of fufu on street with some kind of meat 1 Cedi
Chicken and fried rice in "chop" bar 3-5 Cedis
Pizza in Accra or major city 10 Cedis
Cup of coffee at cafe in Accra 3 Cedis
Small tin of milk 90 pesewas
Packet of Lipton tea (about 20 bags) 1 Cedi
Small tin of Nescafe 1 Cedi (if you like real coffee you must buy it in Accra Mall 4-8 Cedis)
Packet of spaghetti 60 pesewas
Cup of rice 50 pesewas--depending on type of rice
You can buy all sorts of western products at petrol/gas stations all over Ghana, including toiletries, drinks and chocolate.
Share taxi between towns in most parts of Ghana 40-80 pesewas
Charter taxi across Accra from, say, airport to Kaneshie 4-5 Cedis (but not in an official airport taxi, you have to walk down to the road and haggle).
Official airport taxis cost about 8-10 Cedis at least, anywhere (I always walked to the street and haggled). Never ever pay more than 10.
Cheap backpacker room 5-10 Cedis
Mid-range room 10-30 Cedis
Expensive 40 Cedis plus
Visit to the local doctor 2-5 Cedis
Blood test 2-5 Cedis
Visit to well-known clinics in Accra 10-30 Cedis
Packet of doxycycline (anti malarials) that you can buy over the counter in any pharmacy in Ghana: 1 Cedi for about 10 tabs.
You might also want to read 15 Facts About Ghana in which I comment about the old currency and how it is still quoted by most street sellers.