I have LispWorks (I like the IDE) and although the hybbyist, non-commercial licenses are not out-of-reach for many (if not most) people, many (even companies) prefer running on free-of-charge stuff. My current employer doesn't even pay for PyCharm (main language at my current workplace is Python) and they are dirt cheap compared to e.g. Microsoft MSDN Subscription.

I didn't stress the garbage collector enough so I can say that LW is faster or slower than other CL implementations. I'm currently doing an algorithmic research where the strain on garbage collector is not really that big, it's mainly about numerical performance and SBCL is by far the best from what I tried - LW, SBCL, CCL, Clisp, ABCL, ECL. Garbage collector takes usually 1-2% of run time which isn't that bad. I suppose that if I stressed it more than LW garbage collector would outperform SBCL but that's only my theory based on target audience of LW.

If you have experience with Allegro and LispWorks and can compare it to other implementations, could yous hare it, please? I'm quite curious. There isn't much on the internet about this topic.

I agreed with you that sbcl has usable performance (like c and fortran compilers). I disagreed that its performance is state of the art or particularly commendable.

Are allegro and lispworks appreciably better? My understanding was that lispworks, at least, forked from cmucl a long time ago and put less work into python than sbcl did.