I respectfully disagree. Surge protectors and power regulation is necessary in a lot of areas. In areas with heavy usage the power can fluctuate on a regular basis especially if there are brown outs or the power switches across different grid sources. A power conditoner regulates the power which extends the life of almost all electrical equipment. Also some of the cost factor is how many joules( the work required to move an electric charge of one coulomb through an electrical potential difference of one volt) they can handle before they fail and how responsive they are. The better power conditioners filter noise as well as regulate power. Most UPS (Uninteruptable Power Supply) units do not have the capacity for substained operation but merely provide for graceful shutdown.
As far as computer surge protectors costing less, the use a lot less power and are much,much smaller hence the lower cost. Wouldn't it suck buying a low Joule system and have the surge protector fried as well as all you HT equipment if you were hit by lighting or had a significant power surge!
You know, I guess one needs to define their risk adversion and how much they are willing to self insure. You can go without life insurance, you can go with minimum car insurance, you can play risky stocks in the stock market, you can gamble a lot of money on horses. You might or might lose. Such is the definition of "expensive equipment". You are basically saying you will self-insure if the equipment is not "expensive" and provide buy a power conditioner if it is "expensive". Okay let look at pay-back against the silve on-sale $150 HT-15 power contioner. Is a $1,500 system expensive; maybe not but protection is a one tiem cost of 10%. A $3,000 system 5%, a $5,000 system 3% a $15,000 system 1%. LOL add up all your components, in cluding TVs, DVD players, AVRs, speakers etc and you might be suprised at the replacement cost of your system.
As far as computer surge protectors costing less, they use a lot less power and are much,much smaller hence the lower cost. Also some of the cost factor is how many joules(the work required to move an electric charge of one coulomb through an electrical potential difference of one volt) they can handle before they fail and how responsive they are and their low voltage clamping level. Most PC power conditioners are not very responsive but that is not normally a spec you see.
What you should look for:
(1) Response time less than one nanosecond.
(2) Clamping voltage under 400 Volts.
(3) Joule capacityto handle your HT system 5,000 joules is a good number.
(4) Warranty of Power conditioner 1 year, 10 years, lifetime- obviously lifetime is better. ( APC Lifetime : $750000 )
(5) Noise filtering EMI/RFI Noise rejection (100 kHz to 10 mHz) 50 dB or greater
(6) Voltage regulation 120v +/- 15 V
(7) if UPS at least 15 minute capacity.
Now if you live in a perfect world or are a big risk taker then save your $$$ and don't buy a power conditioner. But for most people and since Audioholics has a very nice silver APC H-15 on sale for $150 will will handle all but the most audiophile hungry systems (and those power hungry systems are also EXPENSIVE, therefore they should get two or so), it is a no-brainer
Anyway to each his Own

Peace to those of a differing risk factor and/or opinion.
Later,
MidCow2