Ok, as a rough price guide using Ottawa area prices (yes, this is first hand knowledge and Andy will surely agree with these estimates, more or less).
Milsurp action in suitable condition: about $200.
Machine off charger guide and true up the receiver: about $75.
Weld on aftermarket bolt handle to approximate commercial mauser handle (as opposed to cheaply forging the handle and having it be too short and look like ####e): $75
Buy new barrel in WSSM caliber (remember - these WSSM tubes are all factory chrome lined to prevent throat washout!): about $500 minimum.
Have the barrel threaded, chambered, fit, etc. since nobody currently makes a commercially available WSSM blank pre-threaded for a military 98: about $200, probably more - especially if the smith doesn't have the reamers yet - which is likely since virtually no-one is getting these calibers on custom guns yet.
Drill and tap for bases: $50
At this point, we've looked at all the "essentials" in terms of metal work. We've spent over $1000 and we have a bare steel unblued gun without a stock that may or may not feed because we've not even looked at feed rails and bottom metal yet.
Now assuming you want decent hinged steel bottom metal similar to the Chinese made Charles Daly hinged floorplates on the 798's: $100 or so.
Making the bottom metal anf feed rails work together so the rifle feeds reliably: $50-200 who knows?
Safety that clears scope: anywhere from a $15 left side low swing flag to a $300 (installed) Winchester 70 style swing safety.
Trigger: $50-200 depending on type and brand.
Wood: a semi-inlet will start around $75 for the cheapest and lowest grade wood that will require lots of fitting, up to $3000 for fancy walnut inlet by a talented stock maker. The stock will make or break the gun IMHO.
Now we look at metal finish. Anywhere from $150 for a quick and dirty bead blast and blue (yuck) to $300+ for a proper custom gun polishing and commercial quality blue job.
By the way, we haven't looked at cosmetic add ons like checkering ($200+) grip caps, eboney accents, etc. Plus you might want a bedding job ($75).
Do the math, and then consider a new 798 already in a WSSM caliber sells for under $1000.
As has been oft stated, never build what you can buy.