Butta:

when speed matters...

is 50-100K the total image size per page or per image...

if per image, you need to optimize them (photoshop or fireworks or something else - I think image handler using the other programs referenced in docs etc works but I use off-line tools - fireworks is my favorite)

if you are not using now, check out Firefox with the optional Web Developer Tool Kit and speed report - very revealing.

good questions about what can be done, but the basic approach of optimizing will have big impact, today - you don't lose as much quality as you think (can always have high resolution 'large' image if customers need/want detail etc

my tag line to this is that 'image isn't everything, perception is' - slow will frustrate more than high res will impress...