I went low, about three years ago, with a Schwinn 3rd Avenue, 700C, 21-speed. It was £138 but it came with a lot of good reviews. (Beware of lots of good reviews.) I didn't expect much for that kind of money, so I wasn't disappointed when it came. Out of the box, it looked good. Put it together, and then found neither of the tires would stay inflated, both going down in seconds. The tubes were made of some kind of gritty material and wouldn't take a patch. They were also much too small to fit the tires. Pumping them up was what caused them to burst. The tires had barely discernible treads and were 'hairy.' So down to the bike shop for new tires and tubes.
While out on a ride, about seven miles from home, the front derailleur came loose and rubbed against the chain. The pinch bolt just rounded off when I put a wrench to it, so I had to bend it away from the chain to get home.
The saddle was a piece of junk so I replaced it with a good one. The twist shifters were very poor so I swapped them for levers. After getting mucky rain water splashed up my back I put mudguards on it. Next, I bought a wheel truing stand and a spoke tension gauge because the wheels were out of true. By time I was done, I had a good bike but at a high cost. Then when I tried to part exchange it for a new bike in a bike shop, they refused it because it had to be "bike shop quality." Schwinn was once a good brand in the USA but that is no longer the case.
They say you get what you pay for. I suppose you do, but I sold that Schwinn and went to the bike shop to get my £365 "bike shop quality" beach cruiser. At 960 km both wheels started to grind and I had to replace the ball bearings. Then the headset got me concerned because if I stood next to the bike and turned the steering from side to side, it had what felt like a detent in the straight ahead position. I pulled it apart and found the problem was dirty and inadequate grease. The bearings were good, otherwise. So new grease fixed that problem.
At least I can do these things, myself, and don't have to keep running to the bike shop.