Bigger pixel does not equals to bigger sensitivity, expecially when you compare totally different CCDs - ICX618 and ICX414. For 5,6x micrometer pixels optimal focal ratio is f/20 at which you get max of details. You can go further and get bigger planet image but there won't be more details and the view will start to degrade due to seeing effect at longer exposures. For camera with bigger pixels stronger Barlow would be needed to image at optimal f/36 for ICX414 (you get the same scale and details). If the CCDs would have equal absolute sensitivity per square micrometer of a pixel - then effect would be the nearly the same.
Looking at the CCD sheets at "Typ." max sensitivity in mV and calculating mV per square pixel micrometer you will get:
ICX098BL: 15.94 mV/μm2 (DMK 21, webcam family)
ICX618ALA: 38.26 mV/μm2 (PG Flea 3, Basler Ace)
ICX285AL: 31.25 mV/μm2 (Atik 314L, DSI III Pro, QHY 2 Pro...)
ICX414AL: 8,98 - 11,73 mV/μm2 (the cheap TV camera, used in PG, Unibrain and IDS industry cameras.)
So bigger pixel in ICX414 at optimal focal lenght (f/36) will be probably more than 3x
less sensitive than ICX618 at optimal focal length (f/20). Things like termal noise, readout noise and tons of other things come in here also. Newer design are expected to have less issues with all that stuff. So - it's nearly impossible to "save money" on imaging cameras without limiting imaging capabilities.
If you are McGuyver type and want basic, but good CCD camera for imaging think about modding SPC900NC (or silent clone SPC880NC) webcam. You can even put ICX618 there (40-45 euro for a unit).
http://www.ccd.neostrada.pl/SC3.htm -- those images were made with modded webcam with ICX424AL (like in Lumenera skynyx2.0, Atik Titan). This old mod is described as SC3
There are also simplier SC2:
http://www.ccd.neostrada.pl/SC2.htm (amp off and cooling) or SC1 with nearly no changes
http://www.ccd.neostrada.pl/SC1.htm
Second level would be DMK21, which is faster and less noisy than a webcam. Monochrome CCD at start, and can be modded to ICX618 if someone wants to be a McGuyver.
Third level would be Meade DSI III Pro/no-pro second hand (USA market best, as outside USA the low price is killed by duties and margin at local astro shop
) This has 16 bit, very good sensor and doesn't require modding (except cooling if someone is hot McGuyver).
Between second and third level -
the 2,5 level I would put 12 bit industry cameras supported by some astro imaging software like cameras from Unibrain, example:
http://objectstyle.org/astronominsk/...Sat2008_en.htm Unibrain Fire-i 702 has ICX285 - the same CCD as in DSI III Pro or other astro cameras. To get this cheap you have to usually find a local vendor that makes usable industry cameras. Something for Google searching McGuyver.