I thought that too but the fact that he put up two at a later date means maybe he just put up 20 to test the waters first. Unless eBay has a 20 item cap on a listing or something.

Yeah I personally blame the store for not marking the prices clearly.

Over here a lot of larger chains have this voluntary code known as the scanning code of practice which is basically a policy where if an item scans for higher than the price on the shelf the customer either gets it for free if it's $10 or under or $10 off the lower price if over $10.

Did you buy them?

If it was a small one-man business I'd feel bad and go back and offer to make up the difference. A large chain can easily absorb mistakes like that, although be aware some store managers are nasty types and take the money from the employee's wages. That happened (to someone else, not me) when I once worked at a petrol station many years ago.

Possibly, but he put up 20 at once, so it's unlikely 

Yeah I wonder if they have any more too.

Maybe it's like the case with those 80w Philips 1950s HPL lamps from Canada that the seller listed 1-2 at a time. I think quite a few people on LG got them that time.

Don't think that they are used...but I could be wrong.

Glad I was notified about this sale! I bought one!

That would be good, thanks 

Dont know about US ballasts. With ELTAM ballasts the tap is positioned as :

[P terminal] - 80% winding - [D terminal] - 20% winding - [L terminal]

Then the ballast is wired with L terminal towards lamp when using ES50 ignitor (SIDAC based), and with P terminal towards lamp when using ESPI1000, Steinitz, and some other TRIAC or SCR based ignitors

Also, there are superimposed ignitors, which contain the pulse transformer in the ignitor itself. Those dont need the tap on the ballast at all

I have seen an ignitor which is supposed to connect across the entire ballast (Phase, Lamp, and Neutral). I have no idea what the ratings of that ignitor were, but if i guess, it would be the equivalent of a 2 wire ignitor (with <1kV pulse), except it uses the voltage across the ballast to detect if the lamp is running or not ?