Number Riddle

Date: 1/23/96 at 22:43:31
From: Anonymous
Subject: Brain Teaser...7th Grade

What am I?

1 is 10 cents

14 is 20 cents

123 is 30 cents

943 is 30 cents

I have tried different number systems (bases), tried figuring a 
sequence, but I don't really know if it's a thing or what... I'm just 
plain stumped!

Any help would be greatly appreciated...I feel sure it's a simple 
answer.

Thank you for all your help,

Val

Date: 5/30/96 at 11:31:5
From: Doctor Gary
Subject: Re: Brain Teaser...7th Grade

Dear Val;

This is a very old riddle, I'll give you a hint.

Pretend that you have just built a new house, and want to post 
your new address near the front door.  What would you do?

-Doctor Gary,  The Math Forum