I am a bit biased, I believe canisters are totally over rated, and are not user friendly to clean, so they are not. And there is nothing about being a pressurized can that makes it less necessary to clean.
I also believe sumps are simply better as far as flow, ability and ease of cleaning, and modi-fiablilty.
And as far as cost, mine never cost more than $100 (except the pump)
I run some external overflows into DIY bio-columns if space is tight, or if I don't want the sump directly below the tank. I put a sponge on a column of lava rock, with a filter sock below the outflow to the sump. The sump is then simply any size tank that holds heaters, and the pump, and anything else. Could be extra bags of biomedia, could be a planted area, whatever. Here are some photo examples.
The bio tower, this one is 4ft tall x 8" in diameter (and also fractionates) filled with lava rock as biomedia, $5, PVC to build < $20
its outfall into a filter sock (<$5)
The sump is an old scratched up tank, I got for $3, it also has some biowheels floating around, and bags of media that can be moved to start up tanks, so no cycling is ever needed.
other sumps are planted and basically the same principal
y pumps are usually Laguna's that pump 2000+ gph, and I usually run 3 tanks per sump.