For mtb I usually buy a new frame then a mixture of swap over, s/h and sale bargain bits.
This year I wanted a road bike that was going to be a “keeper”, LBS had a TCR0 at £500 off RRP, took a lot of time setting it up for me, even did my cleat positioning.
2 month check out service (which they let me watch for fettling tips) involved spoke retensioning, gear tweakage, and literally every bolt checked and retorqued.
Sure, I could have done that all myself but I’m pretty naive on roadie tech and it was a pleasure to see my bike practically stripped and rebuilt by a decent mechanic.
Last week had a “mystery creak” , dropped it into shop – mechanic took it round the block, greased and refitted the BB, job done, no charge 😀
Do I feel a mug, not particularly – glad to support a small LBS who let me borrow stuff to try out, give good advice and always knock a few quid off spares……