also paintballers have a nasty tendency to want the latest shiny thing, so when you originally buy your nice marker, one month later a newer shinier model is released leaving you owing lots of money on the first one.
try buying second hand, you will find a lot of top end markers for half their retail price and less, particularly if you can be happy with last years model.
finance is a fools game and the only reason it works with cars is that not so many people have that amount of money to spend outright, however cars are nearly essential to modern life. paintball markers are nothing more than expensive luxuries at the end of the day.
finance companies will offer outrageous interest rates on "personal" items, due to the risk involved and you will end up paying a lot more than the retail when you add interest. try going to your bank and asking them for a short term loan if you really are that desperate for a marker. it is essentially the same thing and they will debit your account the same as say Planet, or any other shop.
take a cheap rate of around 10% will cost you £100 for the privilege of buying a marker at £1000.
have a critical look around you and see what you can do for yourself to raise the cash. ebay some nice but ultimately useless items, clear out the old Dvd collection, lose the ps2 you haven't played in a month. trust me you won't miss them when your shiny new toy is in your hands.