At least according to
a cyclingweekly.com comparison review the estimate of $1000 for a skin suit is an exaggeration. It looks like the top ranked model runs about $202 euros (189 pounds at the moment).
That report attempts to quantify in watts the aerodynamic savings versus a more basic lycra getup. At 50kph the difference between a top ranked skin suit and a typical lycra kit was estimated to be between 19 and 25 watts. Also consider the cost of a typical lycra outfit. Maybe $100 euro for a typical bib and jersey. So we're talking a difference of $102 euros to save around 20 watts at the higher end of racing speeds. People spend a lot more to shave off far fewer watts.
Is it silly for an amateur? Maybe... unless the amateur takes pride in winning and finds him or herself winning more often with a few equipment advantages applied. Two equal riders, with equal fitness and equal expertise, equal strategy and equal mental fortitude, will find the more frequent winner to be the one who expends fewer watts at any given speed. Definitely I would consider $1000 euros a silly price to pay but $202 doesn't sound so silly when you factor in the pricing of alternative common riding clothing.
As for riding naked as an alternative, no thanks. I wouldn't want to cause an accident by people catching a glare off my untanned rear. ...and I think my male-pattern hair configuration would be an aerodynamic hindrance.
Is it silly for a non-racing amateur -- someone who rides just for pleasure, fitness, endurance, etc? Again, maybe not. People who ride for pleasure shouldn't be deemed silly for wanting to do so with nice equipment. And if you're at the end of a 3-5 hour ride you may envy anyone who managed to get through the ride expending fewer watt-hours. When I get down to those last few miles of a long ride my mind often wanders into the territory of thinking about how much better I would feel if I had ridden an even more efficient bike so as to fatigue myself less. I know that is misguided mindset to some extent; a reasonably good endurance road bike is going to beat the rider up less than a top end aggressive racing bike at the end of a long ride. But a skin suit does sound like one of those pieces of equipment with few downsides; you're probably not trading endurance comfort much to get the additional watt advantage.