There are a bunch of cheaper options than the Leica of TLRs, the Rolleiflex, and most will give great image quality when stopped down. What you really pay for with the expensive options is sharpness wide-open.

TLRs are great fun, but quirky to shoot if you're used to 35mm (but therein lies the fun). Some options you might check out would be the Yashica 124 or 124G (no real difference, but the G is more expensive), Yashica A or Yashica 635 (basically an A with an adapter allowing one to shoot 35mm film if you have the adapter). Another option that may be marginally more expensive would be the Rolleiflex's simpler (but arguably no less high quality optics) cousin, the Rolleicord (III, V, Va, or Vb). I've owned and shot with both a 635 and a 'Cord V and in terms of ergonomics, I vastly prefer the Yashica, whereas the Cord has quite a bit better optics when wide open. My 635 is an older one with the 3-element lens, so it gets that weird swirly bokeh that I rather don't like but some people love. Apparently the one with the later 4-element lens is quite nice, but I didn't know that when I was starting out my journey into MF.

There are other options, but these will likely be the most widely available and both are a great blend of quality optics/build without being super expensive. Another issue might be servicing availability, but there are still quite a few people that will work on them, whereas some of the more obscure brands might be tougher to get fixed if something were to go wrong?