There is no reason for HTHP treated diamonds that are near colorless to be a lot different in price from natural, untreated near colorless diamonds. Besides marketing, the treatment is permanent and pretty much invisible. Most of these are laser inscribed "Bellataire" or "GE POL" on their girdles. I suppose there might be some out there without this inscription as it could be polished away or might have been done by a lab working around or infringing on GE's patented process.
I doubt most people can tell a G from an I color so don't make much of that. It takes experience, not a casual look. Don't expect an HTHP colorless stone to be a bargain unless it is from an estate or a distress sale second hand. The new ones are about 15% less money than untreated to begin with so their underlying value is somewhat less to begin with although the marketing plan is to retail them for a premium price....Nice plan, but will it succeed?
There is no reason to avoid these stones. Just get the right price and don't worry over this treatment.