Should I bother.... Yes, no, yes... Yeah why not give my 2cents worth.
From his listing I could probably count an easy ~$35K on accessories/mods assuming everything on the vehicle was fitted professionally and brand new at the time of fitting. $90K would have to include servicing costs, fuel receipts, insurance and reg for the last 10years.
Beside the 90K, the big plus it that it is fully engineered, that's got to be worth a few extra $$$$. The downside is his back yard mods, they look terrible. That second glove box looks wonky. The hole for the stereo... looks like he used an angle grinder. Got to give him points for trying.
Price... A stock 4.2's with around 100K (rare) has got to be worth at least 22K in VGC. With depreciation of accessories, lets say $10K... before you say it, it is twin locked, 35's, Kaymar rear bar which still fetches close to 2K second hand. Aftermarket turbo, long range tank, Turbo, full bar work etc..
+ the engineers... up to the buyer if they would like to be legal and insurable if in an accident.
My price $30K... Would I pay that, no, but had to throw it our their.