The LAW changed on Sept 01st 2007. Gone now are section 16/21 machines to be replaced by section b3's. In lay terms, the new machines must pay all winnings to the bank, cost a maximum of £1 per play, be random and will only transfer a % of your money to plays if you insert a note.
With this in mind, you will now see alot of old section 16 machines appear on ebay as they are now obsolete. machine operators do not want to pay the £1000 plus to convert them as they are simply not worth it. This will in turn, drive down the prices of old style £500 jackpot machines. A good thing for buyers but be warned.... alot of these machines run on computer programs and as such, if they go wrong, you cannot repair them yourself and it will cost £££s to have them done.
Lastly, these old machines are now actually ILLEGAL to use in a commercial setting and the penalties will be stiff. If you are thinking about buying a £500 jackpot machine, try and buy a B3 and not a S16. If you must buy a S16, buy it from a reputable seller and get the owners manual. make sure the monitors are in good order with no burning at the edges. Also ensure that there are no error codes on start up. Follow thus guide or you could end up with a one big heavy, hard to get rid of, pile of junk..