yan nga nasa isip ko...medyo matagal nga...PLUS tumataas din ang LPG kahit na independently mined ang gas sa oil(usually)...dapat may tax break sa LPG dahil alternative fuel sya pero, wala!cibai
If you are too concerned about ROI... don't be. Anyway the conversion recommended for Getz would be the venturi mixer type so it's cheaper than the SGI kits resulting in a quicker ROI period.
Also, if you can put a price on comfort riding in your own car as compared to commuting, maybe the price of the kit would make it worthwhile already.