what's it cost for ECU upgrades under the current rule for high and low end?[/b]
Purely supposition, but they run the gamut. Obviously, the cheapest solution is a marginal cost of zero: don't make changes from stock (maybe bump up your base timing or use resistors to fool the ECU). On the high end, there are rumors of "Motec in a box" costing $3000-5000 or more.

For my NX2000, unless you're wanting to go it alone, your choice is a $450 JWT ECU or nothing (which has been reported to add just about 2 horsepower on a dyno). Another guy offers modified Nissan ECUs and "tune-it-yourself" software (not particularly user-friendly) for ~$300 with all required equipment (mods, upload/download hardware, tuning software).

what would it cost under the new rule for standalone units high and low end?[/b]
Again, it varies. You can get into a Megaquirt system for a few hundred dollars, a Unichip "piggyback" system for $800-1000, an AEM Power standalone ECU for ~$2000, a full-boat Motec system for $3000 or more. The value of each depends on your individual skillsets and motivation, plus what they can offer for your particular car... - GA