I’ve had some very affordable short sleeve ones from decathlon that only say that they are wool rather than merino but are both nice to wear, keep their shape and are robust. Had cheap ones from aldi / lidl (the ones that are 100% merino rather than 30%) but over a few washes they get shorter and wider until you look like a dancer from Fame.
I’ve got a patagonia one that is very fine / thin. Gets all stretched out of shape after half a days wear until you find yourself constantly rolling up the saggy cuffs. Its snags and holes very easily too.
Most used and most reliable for cycling are some jumpers off the sale rail in TK Maxx and H&M for about £15, bought a size too small so they are tight, worn under a cycling jersey – breathable toast.