Well if you do 100,000 miles a year, assume 1/2 is paid, and lets assume 75pplm you get £37,500
If you also assume diesel to be £1.40 per litre and you do 10 miles per litre, then you have a fuel bill of £14,000.
So your turnover of £37,500 is now £23,500... Less insurance, shall we say £2000?, GIT £200 cartax £200, MOT £50 and we're now at £21,250... And we haven't covered tyres, servicing the van, phone, exchange site membership and anything else i've missed.
So a "wage" of approx 20k for doing 2000 miles a week, at least a 10hour day, and i haven't mentioned putting monet aside for the new van tou're going to need every 3 years.
And my example is for 75pplm
Shall we do it for 60pplm?
50,000 paid miles @ 60pplm= £30,000 less fuel of £14,000= £16,000 less ins, GIT tax MOT and we're at £13,750 less tyres, service, phone, exchange membership and you're going to be lucky to get change out of 10k... And where do you get your next van from in 3 years?
And that in a nutshell is why i suspect very few have worked it out... Cos if they did, they'd realise it just isn't worth it