I have a set of extension tubes, cost me $140, and i carry them every where, can make almost any lens you have magnify more, and give you a "cheap" macro lens, i have taken all of my macro shots with my normal lenses with the tubes on them
just be aware though that some lenses, as they have some built in macro abilty, will only focus with extension tubes when the thing being photographed is INSIDE the lens...
my example is this shot...
taken with a 24-70 F2.8L at 70mm using a 12mm extension tube, i was trying to orginally not crop the dandelion, so i was using my 10-22 F3.5-4.5 but while trying to get focus, i realised i was pressing up against the dandelion...
the dragon fly shot was taken with my 70-200 F2.8L at 140mm also with a 12mm extension tube...
so it is a "cheap" way of trying it before you buy very expensive lenses that have limited uses...
M