Well, the RGBRGB models aren't 1/3rd more expensive just for the color wheel. They typically represent more upscale models that add features such as more zoom range, some lens shift, etc.
When a projector with an RGBXXX color wheel is set to most accurate color in its dimmest mode ignoring the XXX segments then, effectively, color wheel speed is cut in half. For each revolution of an RGBXXX color wheel where XXX is ignored an RGBRGB color wheel would be effectively twice as fast. Also when those XXX segments are ignored and no light is coming through it's the equivalent of having three black segments significantly cutting lumen output compared with the RGBRGB wheel that's always passing lumens through each segment.
RGBRGB models also have brightest modes that make them usable in some ambient light. The colors won't be as accurate as in lower lumen output settings but they will be more accurate than an RGBXXX model at the same lumen output. Of course the RGBXXX model can get brighter at its highest settings but at the expense of further color degradation. Most of those extra lumens will be white lumens and not color lumens, so OK for casual viewing but not something many people would consider a quality image compared to RGBRGB.
So, sure, if you just want a big, bright image in ambient light an inexpensive model with RGBXXX can work. But if viewing in ambient light is a high priority then you might be better off with a bright LCD model that produces equal lumens in both whites and colors even at full brightness. The Epson LCD models may not be 100% color accurate in their brightest modes but they do have an advantage over DLP.
I don't denounce any type of projector because each one has a feature mix that appeals to different people. The RGBXXX DLP models primarily feature low price and a usable if far from balanced brightest image. For those who have $500 or less to spend and only want a new (not used or refurbished) projector the RGBXXX DLP models are about the only game in town.
For those new to front projection the decision-making process for picking a first projector can be daunting. For some an RGBXXX model may make sense. For others RGBRGB or LCD may make more sense. All those of us with more projector experience can do is try to lay out all the options and all the pros and cons to help those new to front projection through their own decision-making process.