My soil sampling probe wasn't cheap, but I like it. What I really like about it is that it is a real snap to get samples of just the soil at a 3 to 4 inch depth.
The neat thing about this soil sampler (that I didn't realize was a feature when I ordered it, so I just lucked into this) is that the lowest inch of the sampler completely surrounds the soil core. So, when one inserts the sampler 4" into the ground and then pulls the sampler back out again, the soil that was at a depth of 0 inches to 3 inches can be easily removed from the tool out the side of the sampler. The deepest inch of extracted soil stays in the sampler but can be easily pushed out with a screwdriver and into one's sample-compilation container. This makes it real easy to get a regular 1-inch long core taken from a 3 to 4 inch depth for each soil sample. (I used a sharpie to mark the 4" depth on the soil sampler.)
It takes me about 30 cores to get 1 cup of soil to send in for the sample, since each core is only a half inch in diameter. However, it doesn't take long to get those 30 cores, and collecting so many cores will help give a good average sample for the area being sampled.
PS: If you decide to order the above sampler from Forestry Suppliers, Inc.
, I found that a google search turned up a "free shipping" coupon code, so the cost was only $19.50 with free shipping when I purchased mine a few years ago. Looks like the current price is $19.95.