A small but very pleasant surprise

I bought a software development tool from this company last year, shortly after which they released an upgrade with a lot of very cool features and priced the new version at the same price I bought the old version for (BTW, is it a grammatic sin to end a sentence with a preposition? Somebody told me that a long time ago. Is that true?).

Had I waited just a week, I'd had the much better version without paying more for the upgrade priced at $150 according to their web site. Well, after months, I finally broke down and initiated a transaction for the upgrade. In response to my order, the company wrote me back with a rather steep discount of $90 with no explanation attached! I am obviously not a high volume buyer and only a second time customer, so the unexplained discount is rather baffling to me.

Then why don't they advertise the price at the real price to encourage more people to buy? I am not complaining, but what a pleasant surprise.