Sort of - I definitely have regrets from not buying a bass when I had a chance to. I played a plain looking Celinder J Update 5 in the Bass Gallery back in 2009 I think it must have been. A time when I was selling off quite a few bits and pieces in preparation to emigrate. The asking price was 2250 quid and it was the jazz bass I had been hearing in my head. Full, snarly, crisp and it played like liquid Jesus butter. I've never played a jazz bass like it since.
The only other time I had that experience was playing a Spector NS5CR owned at the time by a BC member who no longer posts on here. It was at a bassbash and I made a mental note to myself to grab it if it ever came up for sale. It did come up for sale and I missed it. Then it passed hands one more time and then came up for sale a third time and I jumped on it. It's been with Mr Shuker for a while to get a slight neck warp sorted but that was my main bass...ironically ever since I stopped gigging.
The last one is Dood's Shuker 6 string headless. We compared his and mine at the LBGS one time - maybe in 2013 or maybe 2009. I can't recall. I remember humming and aaaahing over the spec, wanting something like my Smith but with a little more midrange. On paper, the spec was right but my bass never quite got there tonally. It's a fine sounding instrument but very piano sounding rather than snarly in the mids. I tried Dood's though and it was everything I'd been looking for. How much simpler my life could have been if I'd just asked Jon to copy Dood's spec...but it's not for sale so not totally relevant.