You cant exactly say that its 'considerably' more, but for a person like me or any other 'student' it may/will be a helluva difference.
CG-125's mixture settings can be lowered and the bike will still run like it should, at the cost of quick acceleration.
But Deluxe ... in WORST scenarios, if you drive it hard, i mean like push it, then brake, then again take it 100 and brake ... driving like that, will get you as low as 28km/liter average. But normally, it stays near 30km/liter ... and if you drive it REAL slow and easy, keep it below 50/60 mark ... it can achieve even 38km/liter.
But i haven't heard even a single Deluxe owner going it above 35km/liter.
Do note that if you drive a CG-125 EASY, you can achieve as high as 50km/liter ... which is why i am saying it may/will be a huge difference for a person like me.
Baap ka paisa urana bohat easy hay. Apna paisa ho tub tension nai hoti ... han agar banda kanjoos ho to wo alag baat hay lol 
Like someone stated here before, Controlling CG-125 above 80kms, is really a Misson ... more like a mission impossible lol.
But there is no such thing like that with Deluxe and Piaggio. Probably because of their Large Rear Wheelbase and better rear shock absorbers and their position. But its a fact that Deluxe/Piaggio is the EASIEST bike to handle at higher speeds.
Most people say it stays stable. But i have not experienced it yet so i can't exactly comment on it.
It was the same with my bike until i took it outside lahore and really pushed it to its limits, and found out two problems. The RPM needle starts to jump after 8-9k RPM ... however, the Speedometer stays Stable.
Oh for the love of god dont do that :S
Its not a CG-125 CLASSIC.
The real pleasure of riding the bike is with everything original. However, if you are scared of thieves or dacoits then its another thing.
I own a CG-125 and eventhough i WANT to change it tanki and tapay, but at the same time i dont want to. Why? Because the 'feel' doesn't remain the same. Its still has its original tanki and tapay.
However i am seriously thinking to get some BLACK but GENUINE tanki and tapay to change the riding pleasure. Not to mention that Classic CG-125 looks 10 times better with Black Tanki and Tapay 
Are you serious? Comon ... How can you even compare a 800cc or more "CAR" engine with a mere "BIKE" engine. 
Obviously a CG-125 will be 10 times more economical than a car.
Well you are a Piaggio owner so i can't really blame you can i? Piaggio's engine is advance than Deluxe's which probably makes you think Deluxe might be the same.
But i am afraid IT ISN'T.
The 92KG (Dry Weight) of CG-125 vs. 115+ (Dry Weight) is a clear difference.
If there isn't HUGE difference in fuel consumption, then there is enough to say there IS A DIFFERENCE ... and its certainly not 'hardly 1 to 2km'.
lol
Nice Try 
It wont vibrate. Why "Vibration" was a problem in CG-125? Because it was the sole reason which made it really hard to control it over high speeds .. like someone mentioned ... a MISSION to control it at high speeds.
As per my experience, Deluxe was A LOT easier to control on higher speeds than a CG-125. Heck .. me who is a really bad (not badass ;p) driver, can take it easily upto 120km, and it still would feel like piece of cake.
Are you kidding me?
You Can't just compare them both or can you :S
If it Averages on 30km/liter (given that you drive it on high speeds ... if you manage to keep it down till 50/60 constance, it'll be even higher and CAN be nearly 40km/liter) ... and 12 liters of fuel tank ... that becomes nearly 900 Rupees ... and about 360 kilometers.
A 1600cc car goes for about 13-15 km/liter average on petrol. (if i am not mistaken)
I say its not a bad deal or is it.
Not exactly ... Its certainly cheaper than Petrol and car does more mileage on CNG as compared to Petrol. Difference is not much, but its still noticeable.
Rest remains repairs, well all cars/bikes need it so i will not take it into account. Who cares if the tunning of a Petrol engine costs you 1000 rupees and a CNG's 2000 ... people will remain satisfy because of the fuel mileage /kg its giving.
That issue is quite old now. I dont know if its fixed or not , but i do hope they rectify such issues because its already enough time passed for RAVI bikes in market.
Marketing requires A LOT more money than opening a company or manufacturing bikes. Honda's name is already set so 'no marketing' for them works just fine. Ravi really has some issues whenever it comes to its marketing segment.
I mean just take a look at honda Deluxe ... they are indirectly advertising their EURO2 Standard like they are selling Hayabusa power in a 125cc class. I mean ... seriously ... its pretty obvious for an educated person that they are trying to attract customers by putting EURO2 Sticker ... ahem ... lemme rephrase that ... they are attracting customers by putting Sexy and highly stylish EURO2 Stickers ... which makes most people think if its something like 'best of both worlds' and they just LOVE to purchase Deluxe over any other bike like Piaggio or GS125/150.
But you know ... thats the thing which makes a company money making/sucking machine i.e. HONDA ... ATLAS HONDA to be precise
unn hoon ... dont say that 
ALLAH NASEEB MAIN KARAY 
May i just say that your friends are talking like some ****** bags? lol sorry i couldn't resist.
Apparently they are not ready to accept the change. Comon ... black color still looks hell lot better than red color in Deluxe.
Its only the Piaggio which looks even more sexy in Red 
If it was THAT easy, then why i dont see other people doing it? Especially when come people have time and money to do so but they still dont want to do it. :S