In[1]:= AbsoluteTiming[
 makeList[n_] := NestWhileList[Total[IntegerDigits[#]] &, n, # > 9 &];
 nmax = 7;
 myList1 = makeList /@
   Table[Prime[k], {k, PrimePi[10^nmax] + 1, PrimePi[2*10^nmax]}];
 toCost[n_] := Part[{6, 2, 5, 5, 4, 5, 6, 4, 7, 6}, n + 1]*2;
 listCost[l_] := Total[toCost /@ IntegerDigits[l]];
 totalCost[n_] := Total[listCost /@ n];
 Parallelize[myList2 = totalCost /@ myList1];
 SamsCost = Total@myList2]

Out[1]= {10.3988, 63424722}