Reverse engineering a binary format is dangerous if you are going to ship your reverse engineered codec. They may change the file format w/o warning. However, if you are bound and determined to do it:
One thing you could do is to look at the format for IEEE floating point numbers:
http://steve.hollasch.net/cgindex/coding/ieeefloat.html
And then, starting at the first byte in the file, read 4 or 8 bytes of data. Convert both sets (4 bytes and 8 bytes) to float and double values. Check to see if they match the values that you know are in the file. If so, you have probably found the offset of a price. Print it out, plus the offset. If not, increment your seek by one byte and try again.
If you can find all the values that way, then you might be able to safely patch the binary files at runtime by performing a similar operation: looking for the prices that you know are there, and then modifying the price values in the right place.
This isn't foolproof at all, because random sequences of data will sometimes match up. If you notice a definite distance between offsets, or some sigil that is always present, or perhaps even better, if you can find those offset values back in the file, you may have something modestly stable.