No doubt it's less trouble just to create an 8mm-06--if all the other work involved in turning "an old 98 Mauser" into a sporter isn't included. Personally, if I find a nice old SPORTER in 8x57, I'm not going to rechamber it. But if somebody's happy with rechambering a K98 military rifle to 8mm-06, why then yes, it is simple and cheap.
On the other hand, it doesn't take a lot of money to rebarrel or (cheaper yet) rebore a .30-06 sporter to .338-06. If you figure the expenses both ways, instead of just rechambering, I'd bet the .338-06 comes out about the same.
I have owned an 8mm-06 98 Mauser sporter. It was converted pretty nicely after WWII and I bought it for $225 at a local store. It shot pretty well, too, but damned if I could find any advantage over the .30-06.
