If you haven't bought a ticket to Lund in Copenhagen, you should buy it from special vending machines. Tickets cannot be bought neither on the train, nor at the ticket office. The trip takes about 15 minutes. In the taxi business there roams a wrongly-understood free competition. You HAVE TO ask for a fixed price and agree on the price in beforehand, and ask for a receipt.
Taxicabs normally accept all major credit cards.
A price below 200 SEK can be considered as a normal price, but you may end up in paying more than 500 SEK being a tourist, if you are not careful.