I think it's better to consider what it generally costs to get a camera that has good curtains and doesn't need a CLA, and then compare that against what you paid plus the cost of curtain replacement and CLA for the camera you have. To put it another way, a camera that has guaranteed good curtains and a recent CLA is likely to be more desirable and thus cost more anyway. Anything without a recent service is a bit of a gamble, and one has to accept that there is a risk of an additional spend.
Ultimately, it's about making a choice between the hassle factor of trying various cameras and getting refunds until a good one comes along, or buying one that needs a service and just stumping up the additional cost. With my Leicas (a IIIf and an M2), I took the latter approach.
The IIIf cost 250GBP, and it lasted 3 or 4 rolls before the slow speeds went mega slow - a CLA cost 75GBP, and the curtains were okay (would have been 125 or so with curtain replacement as well as CLA). I still had a further issue with the take-up spool, in that it didn't have enough friction and the film wasn't winding on properly. I'm mechanically adept and was able to fix this myself. So, it took a bit of work with the small screwdrivers by me, and a total spend of 325GBP for a serviced IIIf RD/ST in very good to excellent cosmetic condition. The hassles were the time spent waiting for the CLA, and the time I spent fiddling about with it (worthwhile because it was a good learning process, but important to know when to stop - I decided that servicing the shutter was beyond me, and I don't have any speed calibration gear).
The M2 cost 500GBP in excellent to near-mint condition. The only issue it has is a pinhole right at the edge of the curtain. No sign of a light leak on photos, and the service guy had a look at it when I picked the IIIf - he reckoned it wouldn't be an issue in use. It needed a really bright lamp, with the lens off, to see the little dot of light in the curtain. That was a year and a half ago, and it has been absolutely fine - no sign of a leak on any frame, and I make no special effort to keep the lens covered, or keep the shutter wound or unwound. (I do keep the camera pointed towards the ground in sunny weather, and tend to use the lens cap if I'm not using it for a few minutes.) The service guy also reckoned the M2 didn't need a CLA any time soon - the escapement mechansim buzzes for a little longer than it should on 1 second, but timing is fine.
Everybody wants a low-priced camera that has perfect curtains and a CLA, and it's not impossible to get such a thing, but it takes luck and/or time to get one. It's down to how much cash one has to spend, and whether the saving is worth the time and hassle it takes to potentialy have to check out several cameras.
