Cost can vary considerably with the required geometry and precision. Something that looks simple may end up costing more because of difficulties in holding it for machining (especially if the part is small or oddly shaped) or because it has to be machined in multiple setups (or on a more expensive 4/5 axis machine, which may be more cost effective for a job shop since it can save on the number of setups required).
If the parts are 2D or can be made from a folded 2D shape, then laser/waterjet is going to be cheaper than machining, and some places like OSH Cut will do CNC bending on lasercut parts for what I think is a reasonable cost (haven't used them myself).
If you only need a couple of small parts, 3D printing may be more cost effective than machining, since there's not really any setup and no workholding, and the cost is determined by size rather than complexity. You may have to do some post-processing depending on the required tolerances and finishes, but this may be as simple as just reaming some holes with a drill and/or some sanding depending on the part. I think shapeways will give you an instant quote from a solid model, so worth just seeing what it would cost.
If you do job it out for machining, beware of what your important tolerances are. It's very easy to over-specify a part with tighter tolerances than you actually need, which will drive the cost up unnecessarily.
It may also be worth looking around for a local shop, a small place that can fit your job in around other work may be able to give you a better price than one of the bigger internet places, especially if you aren't too picky.
Finally, there are some places like
https://100kgarages.com/ where you may be able to connect with someone who has the equipment to do what you need. I've never used that either so can't vouch for it, but if it's a hobbyist who's just looking to cover some project costs the prices may be better there. Again, it'll be easier to get a good price if you're not too picky or in a hurry.