can anyone give me any idea of current food/restaurant and drink prices in Costa Teguise

As a general rule in Lanzarote you will find the following...
Food/drink in the shops...
Most foods similar in price to the UK or slightly more expensive. Wine, beer, spirits cheaper. Meat (chicken, beef, pork, lamb) more expensive. Avoid UK brands as these are significantly more expensive, buy Spanish brands.
Restaurants...
Main course costs anything from 7 Euros upwards depending on the restaurant. Typical mid-range meal, for 2 people, of 2 courses with drinks would be around 30 Euros.

cost of a taxi from the airport to Costa Teguise

15 to 20 Euros.