Sailplane or glider is taken to be the same thing these days and has nothing to do with whether an engine is fitted or not. Some sailplanes are capable of self launching, some only self sustaining, most are not fitted with engines. The trend today in new purchases appears to be towards self sustaining or self launching.
UK prices late 2009 range from around UK£5000 for a late wooden aircraft to UK£200000 for a new top of the range carbon two seater. A good, still competitive, single seater around £50000 but you can get into the sport competitively in club class for around £10k - £15k, the cost of a two or 3 year old quality family vehicle.
Flying club aircraft will keep costs to around £1500 - £2000 per annum including flight time and club fees in the UK. In the UK, South Africa, Australia, New Zealand and a lot of other places Instruction is done for free by club pilots saving on training costs.
Some interesting sites with classified sections
www.gliderpilot.net and www.segelflug.de