High margin? You're definitely not talking about the ISP market in New Zealand.
Here we go. So they are struggling and there are so many business masochists around, who'd love to struggle and operate on break-even line, which cause so many of them do register new ISP companies every year.Imagine when somebody doesn't want to pay full price for their internet for a few weeks...
Imagine when you fill the petrol in your car and pay for a full tank, but just a few times it fills 2/3 of the tank. So this shouldn't bother you or why does it have to? It might be still filled full on the next time you pay, so no worries.
If you think the RSP world is full of companies making inflated profits you really have no idea of the realities or margins involved. That's all I'll say of the matter. The sale of Orcon twice and even Orcon admitting it took in excess of 2 years to make profit on a EUBA customer is all the proof I need to present. If you don't believe me that's fine - you can live in your own fantasty world and feel hard done by each month if you feel you're being ripped off.
Why are new RSPs entering the market? In some cases because they're small players simply reselling wholesale services who think they can make a quick buck. The fact there are now far fewer RSPs in NZ than there were 5 years ago is the proof that many can't make money so they simply sell.
Your petrol analogy makes no sense. Copper is a best effort service and it's fully explained why speeds will vary on copper. Buying petrol has absolutely nothing to do with this.
Anyway I'm out of this debate. Good luck trying to resolve your problem, I would have helped and offered you plenty of advice on why sync rates would vary and some very likely causes but I'm not interested now.