I had a retul fit a couple of weeks ago (£150), and done a few hundred miles since then, including 72 on Monday and a hilly (for me) 47 miles yesterday. I have all sorts of bio mechanical issues down my left side mainly, some historical and some following injury/surgery earlier this year. Main symptoms pain in knee (not surprising as I have two meniscus tears and mild-moderate arthritis) and low back pain, around kidney area. My physio has diagnosed this as sacroiliac joint pain, common in cyclists. I am not what you call flexible and have history of back, knee and shin surgery, and elbow surgery, on the left.
For me the aim is comfort on the bike, and not achieving speed, pedalling efficiency, which seemed more the fitter's aim. The two probably are linked and also, perhaps a feature of where I had it done and by whom (a race oriented shop, and a guy who races).
The fit included, putting up the saddle around 60mm, adjusting saddle angle and position, flipping the stem, adjusting cleats, i think he slightly adjusted the tilt of the bars too.
Has it helped, hard to say really at this point. I have put the saddle down a bit as I simply didn't feel safe riding in traffic and especially having to stop quickly in traffic. I need to be able to get my foot down, without my toes cramping! The pavement isn't always available as a foot rest!
I have had quite a lot of foot pain, numb toes, although this was better yesterday. I have emailed with the fitter about this, he says I need to get used to the position which he says is correct, again for efficiency. I am persevering. This had even started during the fit while pedalling on the turbo. I also need to wear orthotics so my feet aren't perfectly formed either!
To the OP, it is certainly worth a try. However, if you can't really afford the actual fit, could you afford to change component, stem, bars, cranks, or heaven forbid be told the bike is actually the wrong size. I knew my bike size was ok and the components, although the bike fitter did say initially that he would probably would have fitted me as a 56cm rather than 54cm, but after the fitting process he was happy all was the correct size.
oP - I would also see a physiotherapist in conjunction with the fit, or find a fitter who is a trained physio if you can, get an exercise/stretching programme, given your issues, look at core and flexibility
I am in the middle of an ongoing rehab physio programme so I think only time will tell for me, there are however a lot of variables, so I may never know whether the fit was worth it. The experience was interesting however and the cash aspect wasn't a deal breaker ultimately