Given that the total budget (over KoP) for an FRC robot is $4000 (R10 this year), it will rarely be the case that a sensor that costs over $100 will be cost effective. The one common example I can think of is an IMU (integrated motion unit) which really merges several sensors with a lot of processing.
For FRC range finding purposes, I have found relatively inexpensive IR sensors to be great for short ranges (up to 80 cm/30 inches) and ultrasonics for mid-to-long ranges (20 cm/8 in - 10m/30+ ft). If you really need something that includes both short and long ranges, often a combination of two relatively inexpensive sensors can be as effective as one higher-priced one.
In general, when I find that we are planning to spend more than about $25 on a single sensor, I make sure that we (and usually I) have spent several hours searching for a less expensive alternative that will meet the requirements. The great majority of the time, we find one.
Also consider cameras as range finders. If you are looking for a known-size target, can send two parallel laser beams, or can exploit some other geometrical tricks, you can use the size/separation as a range finder.
Edit:
Quote:
Originally Posted by DonRotolo
Don't decide on a technology until you clearly define the problem to be solved.
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Second Edit: for off-season experimenting, I suggest being a bit more frugal than you would be during build season. There's more time and less risk, so try to learn to work with (and find the limits of) less expensive sensors before investing in the high-end ones.