Despite all the garbage on a lot of forums stating that nobody ever pays for business or first class, I'd venture a lot of people on most airlines pay for their business class ticket on long haul flights. As for me I always pay for my business/first class ticket for work and liesure and use my miles to upgrade family/friends. I wouldn't necessarily buy a business class ticket form SYD-MEL, but long haul flights (especially on 14-15 hour) flights are especially exhausting in economy when there is high loading (and most airlines are making sure they are getting over 80% loading in economy on all routes or reducing frequency). For work I need to be refreshed when I land, and for liesure its nice not to have to spend a day recovering from a flight. I try to travel as economically as possible. For instance I just won't go out and pay for a 18,000 AUD first class ticket. As with anything travelling in premium cabins requires some intelligence and planning. Here are some things I used to secure a good deal:
1) I know a competent travel agent. Travel agents even though they have been relegated to glorified holiday package salespeople can still be of enormous help with airline tickets. Good travel agents are the first to know about airline sales, promotions, special fare tricks etc. While I know relatively a lot about certain things with air travel, my travel agent knows 100 times more. There is a downside to travel agents, as airlines are trying to push them out of the equation they are making internet only deals much more common. Travel agents will likely not have access to these fares, and will know nothing about it. Airlines seem to refuse to let travel agents know about online specials.
2) I use a few travel tools, and plan my flights (if I can) as far in advance as possible. As I'm in a field that has much more flexible time frames, I hardly ever have to book last minute tickets. Booking in advance doesn't necessarily give the best deal, but what it does do it allows you to be there when a promotion or sale is on. For instance a business class fare to London for departure in June of next year may be 12,000 AUD, but if you wait the airlines usually release a special fare that is up to half price. I map out all my flights within the next year in my calender, and I input them all into KVS/ExpertFlyer. For flights I haven't booked yet I will do daily price searches (these tools allow you to save searches so its relatively easy). Generally these tools show internet only fares, but sometimes they don't so every so often (every week), I'll go to the airline website to do searches. I also check on pricing of tickets I've already purchased as a lot of airlines will give you travel credit for future travel on the difference if its a similar booking class. I know this procedure is quite obsessive, but one thing airfares are not is static. A lot of airfares I've secured over the past have only been available for a week or less.
3) Sometimes using creative routing is key. I remember when I was in the US for a year, and I had to go to Taipei. The cheapest airfare was like 12,000 USD first class in 1998. I did multiple multi city searches with *A carriers and found a first class fare going through BKK and then Taipei on United and Thai Airways that was 6,000 dollars cheaper. When do I do these creative routings when the fares of certain routes are above my threshold. Sometimes traveling short-haul in economy to a different starting city can reduce the fares markedly as well. (Example sometimes fares ex Melbourne or Brisbane are much cheaper than Sydney).
So yes buying business class/first tickets is more expensive than economy, but if you play it smart it doesn't have to be the eye-gouging prices you normally see if you just did a random search for business class/first class airfares on a travel or airline search engine. For my money, paying 4000 to 6000 dollars more for a 24+ hour flight to have some level of personal space and comfort is well worth it, especially as I travel relatively often. In all honesty whenever I am flying in business and first, and go back to economy just to look I am disgusted how airlines have to cram people in to make money. It would be nice if somehow airlines could still make money, offer reasonable fares, and allow better space for passengers. Unfortunately I fear that its part the travelling public's fault as well which expect cut-rate fares. I would think even an increase of fares by 20% would allow some more space in economy, but passengers would probably flock to the airline with crammed in seating for 20% less.