rottcod
UK clubs are subject to Corporation Tax if their visitor income is over some minimal figure. You are allowed to allocate course costs against that income, in proprotion to the number of rounds played by visitors vs. members. The club pays something like 20-25% tax on the net income. At the club for which I was Finance Convenor the tax came to about 5-10% of gross visitor revenue.
Tom P, Bob H and CraigD are right and they are wrong. Yes, UK and Irish clubs are quite happy to have visitor income to keep dues down, but it is a stretch to say that this is why dues are so cheap on this (European) side of the pond. Even if visitors were completely banned, at the clubs I'm familiar with (including one "name" one) the dues for members would only go up by about $200-500/member. Now this is a big number to many of these members, as the normal dues only range from $300-500 per year at these clubs in the first place. Compared to any comparable US clubs, however, to total numbers are trivial.
I do believe, however, that because of the fact that many of our most favorite UK clubs have found out that they can in fact charge extremely high fees to (mostly) American visitors, that many of them have reached the point where they do not need any more visitor income. In fact many feel like they "have" to spend increasingly large surpluses on increasingly foolish projects just to keep the taxman from taking more money away from them. These high fees have had the effect of driving the ordinary "punter" particularly those golfing societies of which Craig speaks, away from the "name" courses and onto the more modest ones. They are also causing members at those name courses go more and more down the Muirfield route, of limiting visitor play only to that amount that meets some sort of minimum income requirements.
As a result, I very much believe that it will be harder and harder for visitors to get tee times at the name courses, and while I do not expect these courses to become as exclusive as US private clubs (or Swinley Forest), I do think that days of being able to walk up to Sandwich or Muirfield or Troon or Hoylake and get a game almost immeidiately (as I was able to do 20-25 years ago) are gone and unlikley to return.
They will keep letting on visitors, however, becuase, as others have mentioned, this is part of the ethos of clubs over here. They are proud of their courses, and enjoy sharing them--even with strangers. This is a fine quality, and it is a pity that so few private courses in the US seem to have the same attitude.