This week no rambling intro. Straight to the point, grasp the nettle, strike with a hot iron, no beating around any bushes - that sort of thing. Focused. And why? Because I've been doing a lot of thinking over the past month about restaurant prices. I've said in this column that they seem to be rising remorselessly, but you could reasonably ask me what are my criteria for a judgement of 'expensive'? The answer is both simple and complex. But to begin at the beginning: if you go to a lot of different restaurants you soon get an idea of what is available and at what price. What is interesting are the discrepancies that you can find between restaurants.

In early January, I ate in a restaurant called Pearl Brasserie, where the chef/patron is Sebastian Masi, the chef for five years in The Commons while they had a Michelin star. Take it from me, he's a very good chef who makes wonderful food. So the question that was exercising my mind was this: if Pearl Brasserie with its excellent food, city-centre rents and city-centre rates can keep main courses for dinner under £15, how come less accomplished restaurants feel that they can justify main course prices of £18, £19, £20 and over? Is it simply that there are people willing pay it? In truth I can't answer that, but I can answer my first question. With Pearl Brasserie as my base-line, I have a measure against which I can assess what's expensive.

If you think that the expense of the ingredients is the solution, it doesn't work very well, as the cost of the raw ingredients can be a little as 20% of your bill. The rest is made up of fixed costs: light, heat, wages, rents, rates, servicing loans and so forth. But there's another element as well, the profit margin, and that can make a significant difference. Take soup as an example. Even if it's made of seafood you'd still be hard put to get the cost of it to much over a £1 a portion. So anywhere between £3 and £4 is how you'd expect to see it priced on a menu - and, check it out, that's pretty much what soup costs everywhere. If it goes to £5 or £6 for something like an onion soup, then in my opinion it's over-priced - unless you're in a dining room of exquisite elegance with perfect service.

What it comes down to, as ever, is value for money. If you're lucky enough to have a company credit card with bottomless funds, that's one thing. But if you live in the land of ordinary mortals and spend your own hard-earned cash, you notice when prices begin to bite. Which must be why, when I went to meet to meet my friend Miriam Thornton and her friends in Mario's of Sandymount, the place was packed. There were five of us, all except for me young, trendy and urban. Miriam, and Frances Clune from the not so urban Feakle, her friend Jonas Dalin and Kieran O'Reilly. I'd come through a Wicklow snowstorm to get there and was delirrah and exirrah to have arrived in one piece. The jackeens had no concept that beyond their urban world there were six-foot drifts that made driving the sort of thing that Finns enjoy in the winter.

Mario's is on Sandymount Green, just a few a doors from Borza's, one of my favourite chippers. It's a long, deep room with loads of tables and lots of people eating and drinking and having a good time. Small tables, densely packed, comfy chairs and the buzz that you get from a busy restaurant that's clearly giving people exactly what they want. It has a simple menu with starters like bruschetta, garlic bread, deep-fried mozzarella, garlic mushrooms and crostini; there are pizzas and pastas as well as a few red meat courses and plenty of chicken choices. Starters are all around £4 and pastas and pizzas clustered around £7-£8.

The wine list has about twenty reds and twenty whites, which is plenty, and Italian wines are well-represented. House wines are very reasonably priced and the majority of the list is centred around the £14-£15 range, which is very fair. Despite the varied choice in Italian wines, I chose a couple of Australian wines; a Wolf Blass Shiraz red at £15.25 and a Lindemans Chardonnay at £14.50 while Kieran had a couple of Italian beers, the Peroni Nastro Azzuro.

For starters Frances and Jonas had picked a bruschetta between them; Kieran had a minestrone soup; Miriam had the deep-fried mozzarella and I had the gnocchi in a cream and Gorgonzola sauce. These were all good, tasty and generous. Not faultless, but at these prices you wouldn't expect them to be. The next courses, which consisted of a tagliatelle with a seafood sauce, a spaghetti carbonara, a chicken diavola, spaghetti Bolognese and a pizza Molicone for me, were also good. Incidentally, the Molicone was similar to what is often described as a Cappricciosa. None of this was haute cuisine - but it's well-made, served with efficiency and politeness and very reasonably priced. We finished the meal with a couple of espressos, a couple of decaffs and a couple of cappuccinos.

While we were sipping our coffees a thought struck; this was Ash Wednesday, Non-Smoking Day, and about two thirds of the restaurant at a rough count, were smoking. Curious. After a second espresso for me we got the bill, which came to £95.85. When you've had good food, drunk decent wine and been well served, a bill of £20 a head comes as an added bonus. I'm told that Mario's can be found in Ranelagh and Terenure as well, presumably much the same. I'm not normally a fan of formula food, but I have to say that this is a formula that works and works well. I left Mario's a very contented punter.

A few weeks ago I reviewed a restaurant in Clontarf called Liaison and they have since been in touch with me, believing my review of the meal I ate there to have been 'unfair'. They called my attention to errors of fact in my review. One, that the bottles of mineral water on the table were not half-litres but full litres. Two, in commenting on the wine list I said that the page listing Bordeaux had no wines under £28. This was incorrect - there were in fact four. I should have written 'no wines under £20'. I accept that this may have added to the impression that I gave in my review that Liaison was expensive.