Yeah, most of the residences in the game are not realistically priced. A mid-floor apartment in Sierra Towers(Eclipse) goes for $3-5 million in real life, depending on condition and layout. In game they go for ~$370k-$1m. A knockdown in the hills goes for ~$1m, yet Hangman Ave is $175k. You can't buy an 1/8th of an acre with a canvas tent on it anywhere in LA county for that. Move-in condition detached home north of Sunset is 1.5m if you're west of I-5, and that moves up to about 5m once you get west of Laurel Canyon. A knockdown in Watts(picture Franklin's house at the start of the game, but located in the worst part of town) goes for $350k. A home similar to the 10 car options they added in the hills a while back(stilt houses) in the area is going to start at about $3.5m. Another example is the purchasable house at 2868 Hillcrest Ave in game for somewhere under $800k(I forget the exact amount); the home in real life is 1873 Sunset Plaza Dr and is currently valued at ~$3m and it's very spartan for the area.
R* doesn't seem to price items with any relevance to real life, but it seems rather to the demand they think the item will carry with online players. As opposed to the above residential property disparity, you can perform a hydraulic suspension conversion for a couple thousand in real life, but R* wants something near $1m for certain cars....
That is one reason I think for the low yacht price, is that in game once you price something that isn't perceived as a necessity above a certain point most players will pass on it. Even the wealthy players will often pass on a high priced item with limited use. That is why there aren't many Gold Luxors, but plenty of yachts. If the yacht was priced relative to the Luxor, there would be very few of them.
A Learjet 60 runs in the mid-high $3m range(as opposed to 10m for the luxor Deluxe) whereas in the yachting world you will spend well over $50m to buy anything over 200ft built in this century. For a new build similar to the Pisces or Aquarius? Plan to put down $200m before the builder will lay the keel, and be ready for another $100m after launch for outfitting.
The economy has also changed quite a bit in the time the game has been out. Upon initial release, a fully decked character with every purchasable item in game, 9999rds of ammo on everything, a couple of $400k apartments with a few supercars in there would run you between $18-20m. You could make ~$450k an hour with Violent Duct and some others. Now, to own a full roster of properties with full garages of modest cars, all the clothing and purchasable items, ammo, etc; $100m is a starting point, and I'd budget closer to $150m. You can make about $200k/hr doing VIP stuff regularly, and just a tick under $500k an hour on the final heist. So the cost to maintain the baller lifestyle increased something like 8-10 times since the game was released, yet effective 'pay' was reduced. I guess R* does follow real life!