Our competency on projects where we are being paid a full domestic consulting rate is quite high, thank you.
Now, if you're asking us to compete with cut-rate bids from some online freelancer exchange, we will reduce the level of service and QA to match our competitors in that space....
Eg. you may have Nordstrom's service for a Nordstrom's price. Wal-mart service for a Wal-mart price. But don't expect Nordstrom's service for a Wal-mart price; that usually isn't going to fly....
You can insert ImageMagick somewhere into your production pipeline. It's excellent software.
[1] Like MVG (http://www.imagemagick.org/script/magick-vector-graphics.php) and MSL (http://www.imagemagick.org/script/conjure.php)
For JPEGs: use chroma downsampling, and don't go above 80% quality unless absolutely necessary. If your software has a preview function, use it. Encode with MozJPEG if you can.
For PNGs: compress the hell out of them. There's several tools that can compress them further.
You still need to resize your images appropriately but ImageOptim will do the rest. It passes images through a series of image optimization libs.
This is such a trivial optimisation it makes you wonder about the level of competency of the average web development company.