I sell them for 44r each, on SMP9 at 19000. I have plenty in stock. I'll even deliver them to you (or a chest) on SMP1, if you want. 300/44 = 6.8 so, you could buy 6 (for 264), and have enough change for a stack of arrows and a chicken spawn egg, in the same shop. You might get 'em for a few r less, maybe save up to 30 rupees, if you spend enough time shopping around. Then again, in that time, you could go and e.g. chop down 3 trees and get 50r worth of wood.
P.S. EpicBobMan, it sounds like you could use a few extra rupees; try these; http://empireminecraft.com/rupees/promo/zjinx http://empireminecraft.com/rupees/promo/zomfg http://empireminecraft.com/rupees/promo/z3ett http://empireminecraft.com/rupees/promo/zdddy