I paid about $550 for replacing timing belt at a dealer. I don't know if this is fair enough, but I think that it should be professional enough for the rest of my car's life.

Dealer in SD was $314 in parts and $356 in labor to:
replace Serpentine belt, timing belt , timing belt tensioner, and timing belt pulley.
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1993 240 Classic; 1992 240; 1997 850 GLT; Mitsubishi 4 cyl.

I'd say about 2 hours labor plus parts. I have a 94 850 and that runs about $225-$300 at local volvo indy. Depends on if the decide to do pulley - which is about every other change.

I bought a t/b, serp belt, water pump, idler pulley, tensioner, ftont cam/balance/crank seals at FCP Groton. I took the parts and copy of Bay 13 t/b how tos to my mechanic and he replaced all the above for $300. I took the how tos because he doesn't work on Volvos.

I'm no expert but the t/b, w/p, tens & pulley appeared to be in excellent condition at 97K. Though I'd still change the t/b at the prescribed interval
98 S70 t5 bought with 97K on the odo.

In Memphis, $800, at an independent shops in central PA, $600. Part are $150-$200 and you could do it yourself, if you have the tools and above averge skills. Good Luck