This is part answer - but also number of questions - as answering these will help steer you towards a possible answer. You can do the following to see if a Canon + CHDK solution is what you want -

You say that you used a $70 Canon camera. If that is a current camera and a new price it may be less suitable than an older model with more appropriate specs obtained second hand. I buy used Canon cameras here at auction (local ebay equivalent) for use with CHDK. Prices are typically $20-$50. Modern cameras tend to have higher megapixels (MP) but often worse noise. At a given shutter speed they may be noisier or for a given quality may need a lower shutter speed.

Camera settings overall need to reflect what you are trying to do. Full auto is OK if you have plenty of "latitude" and the photos achieved meet your needs. If they don't - which is the case here - you need to know what settings the camera is using, so that you can tell what can be altered to improve results. Large apertures (small f number) allow higher shutter speeds but quality usually drops off somewhat at full aperture. High shutter speed reduces the effect of vibration but on full Auto may cause high ISO or large aperture (or both) to be selected. Increasing ISO generally improves ability to resist vibration but introduces more sensor noise. Max acceptable ISO varies widely by camera.

The camera needs to be "given a chance" to work well. Rigs that I have seen in commercial use have used vibration isolation to limit transmission of vibration to the camera. These may be spring suspension arrangements or foam padding and similar. Such systems may allow vibration or oscillation in the mounting and a degree of damping may be needed. On a conventional style model helicopter DSLR carrier I was told that they had tried many models of DSLR and that some worked better than others. This MAY relate to anti-shake/antivibration control but also maybe other factors. Canon powershot cameras probably don't have anti-vibration control, but note that this can work against you in some cases.

To get good quality you want

• Camera with best noise performance (older with less MP MAY be better)

• Higher shutter speed (so low noise camera desirable)

• Preferably not maximum aperture (ie not low f number)

• Maximum ISO that works OK sensor-noise wise.

• You need to be sure that AF is enabled and that focus is occurring
  OR that you are in fixed focus mode with focus distance set to the hyperfocal distance or better (ie sharp across whole range of interest).

ie you need to be sure that you are using a CHDK capable Canon camera that meets your need reasonably well, and that it is set up well.

• By performing on-the-ground tests with no motor vibration or flight movement you can test camera settings and how well it works in optimum conditions.

• You can use an image editor to inspect the EXIF data in the photos to see what camera settings are used.

• You can use CHDK to set the camera to its optimum settings

• By comparing better and worse shots and their EXIF data you can determine if there is any obvious pattern.

The EXIF data is available from many free or paid image editors - usually including one that comes with the camera.

Questions:

• What model of Canon camera are you using?

• What ISO settings and aperture are you using?
  Manual or automatic settings?
  What sort of EXIF figures if auto (perture, shutter speed, ISO, ...)

• How do the best photos compare with ones taken at a similar range on the ground handheld - ie no vibration.

• Are you using AF?
  If AF is used - does it seem to be focusing correctly?
  If manual focus, what focus distance are you using, and why?

Report back. Ask questions.