First, you say get lighter components to compensate for the additional weight, i.e. saving 3kg. This is very difficult and would mean replacing a lot of components, almost all including fork and rear triangle for the titanium version.
What of course would cost much more than 500$. In average, one gram saving cost one €.
So, you won't be able to keep the weight as it is even with a lightweight, 3kg, electric assist. Your bikes will become more heavy with their electric assist.
The "cheap" components that allow to save weight are, first the tires but lightweight tires are also more puncture sensitive. The amount of weight saving depends of the tires you currently have.
Then, the pedals, using one side removable pedals (better with titanium axle) save a lot compared to the original pedals.
Next, the saddle, using a full carbon saddle weighting less tan 100g saves a lot even more if you have a Brooks saddle.
Then the seatpost. A titanium without pentaclip seatpost (Brompfication type) saves also a lot.
With the electric assist, you can also consider to convert to an external 2s (or 3s) without the 3s internal gear hub. If you do this, you can use 11s compatible sprocket and use a lightweight KMC 11s chain.
You can also either remove the mudguards or use the titanium parts of the superlight Brompton for those mudguards.
Further weight saving are possible but save less (front wheel, brakes, brake levers, bottom bracket, hinge bolts, all bolts for titanium...)