The $10 one I saw had an output.
Like I said, I'd like to see a side by side comparison.
I have a box of these, ranging from "$10" (really, $60) to $300. The two I use are DrewTronics and
SlavTech.
Almost all "hobby" grade probes use the design with three mechanical connections (a dowel pin makes contact between two balls). As far as I know, this is an old Reneshaw design that is now out of patent protection.
DrewTronics probe is very simple - a resistor and an LED, that lights up when the circuit is opened. SlavTech has some circuitry, but works on the same principle. Both give me repeatability under 0.001" (I have "alarm" set to 8 microns, and rarely see the warning). Both are very well made. I talked to both owners (Andrew for Drewtronics, Slavomir for SlavTech) and they both were knowledgeable and responsive.
I don't know about $10, but Chinese probes in the $80 range (that I own) are "OK" if you get lucky. Cheaper parts, a bit slippy built, etc. but mostly functional if you get a good one. Out ot 5 Chinese units I have, one was dead on arrival (missing solder joint on the connector; an easy fix), and one has weird "jitter". The contact spacing is uneven, so the stylus doesn't make solid contact. Repeatability is a bit worse (I often get 0.0016" spread on the "best" one).
As far as side-by-side comparison goes:
- DrewTronics - made in the USA by a small business, and is objectively better quality than the Chinese probes I own. Has warranty, and the owner of the company picks up his phone and talks to you when you call.
- SlavTech - made in EU by a small business. Quality and "presentation" about the same (I like the connector and longer cable, but the body is not anodized). The owner answered my email right away when I had questions.
- $10 Chinese probe - haven't tried
- $80-ish eBay probe - made in China, QA doesn't exist, works if you get lucky. Support for the two that had problems was along the lines "please send pictures; please send a video; there is no problem; you're just using it wrong; send it back to China and we will look at it; please remove the negative feedback and we will give you $5; please close the eBay case and we will refund you."
On a personal note, I get questions along the lines of "why do you charge $130 for your DIY DRO adapter; I can get a whole unit from China for $80" almost daily. The short answer is "Because I don't use slave labor, Chinese government is not subsidizing me, I've spent a lot of time and money on R&D, I pay for good quality parts and assembly, I inspect and test each board, and I stand behind my product".
I suspect the answer to your question about $10 Chinese probe, vs. DrewTronics is about the same.
Whether or not it's worth the difference in price, is a personal question.
Regards
Yuriy
P.S. I am not affiliated with either company, and bought both probes for full price. 
