Instead of refilling cartridges I'd suggest go in for lower cost compatible cartridges.
Among the three, original equipment manufacturer(oem), ink refill or compatible cartridges, the last one is the ideal option. Taking into consideration the cost---hands down refill and compatible cartridges trump over the OEM. But most users claim (due to ink refill), that they experience consequences. i think this would be due to the refill (rule of thumb: only refill a cartridge ONCE. More than this and you risk diminishing the quality of the printout and damaging the cartridge and/or the printer itself)
I get my HP ink cartridges online. Aside from HP, you can find a variety of compatibles like epson cartridges, cartridge discount laser minolta toner, tektronix 7300 printer ink and pitney bowes fax toners. Luckily, I have yet to go through any of the consequences that other consumers have experienced with regard refilling and compatibles.
With these items raised, my money would be with the compatible cartridges.