The performance figures you quote are about right and that is why Fiat immediatley repsonded with the Strada/Ritmo 130TC. This car did knock the Golf of its perch.
The huge difference with the 130TC was the large but absolutely near flat torque car. This made it, for its time and just about still, the best open road point to point driving car.
Once the carbs are correctly set-up and balanced then many German press tests go 0 to 100kph (62mph) in 7.5 seconds. For me I don't give a monkey's about 0-60 times. What is difficult to measure is real driveabilty, point to point, etc.
Track tests did always show the 130TC beating the Golf GTI but that is and unfair test and comparison for BOTH cars.
The later Golfs nailed the performance moderated by end user acceptability / driving comfort
The 130TC basically went for all out performance, handling etc. and with that came firm/harsh ride, heavy steering at low speeds and a load of other "not a family / everyday car" attributes.
The 105TC was a car just a little too early for the hot hatch market and when the Golf GTI appeared it was too late/solidly in production. The 130TC was a post Golf GTi response, too aggressive and too late to stem/stop the Golfs rapid rise in sales.
Is the Golf GTi a great car - absolutely YES - proven by history in terms of sales, etc.
Is the 130TC a better car - YES, in my honest opinion, but there the story ends unless you are a dedicated enthusiast and have actually driven one. Those that have, even after driving the Golf GTi, will attest to the 'extra special' 130TC ..........
Moving back to the original topic about 105TC value, much of the 105TC trim is the same (or near enough) the same as the 125TC/130TC models. This is what makes the spare parts value (for both 105TC and 130TC cars) very important.
The problem/difficulty with the spare Strada/Ritmo spare parts scene is that there are so few cars left out there. However a top notch original condition 130TC will/should be insured on an agreed classic car policy for a minimum of say £5000. (NOTE! there are very few of this quality level).
Lets follow this through.
Your 105TC/130TC is insured for and agreed £4000. You get hit taking out the rear quarter panel (no longer available so has to be hand made) and of course the side moulding that extends over the wheel arch to bumper. A classic car body specialist can hand form and create one of panels in the absence of a mould/press patern.
Sadly plastic body mouldings (or any moulding like wheels) can not be economically reproduced if the original moulding are not available or have been reproduced.
So a rear quarter panel created from scratch costs say £500 to £1000. A large trim moulding would cost probably £1000 for mould creation alone. Now you see where the real value in rare spare parts comes from.
Car buyers look at the overall car, overall Glass Guide/Parkers Guide prices and totally forget that for many cars out there the real value is in the parts and not the car.