Final Upgrade still x17/x10?

My theory is that it was purchased from nery's, where the base repair is 12 for 95% and 32 for 98%. If you either took the durability upgrade first or the final upgrade is x10, the numbers almost perfectly match.

If you apply the upgrades in opposite order, and round down each time except for the final, the numbers match perfectly except for edern, who's off by one. I'm still trying to figure out why.

If you take the repair prices and divide them by the base price, they come out to almost 83.

1. 90 : 83.521
2. 95 : 83.333...
3. 98 : 83.4375