When you buy a vehicle is always wise to get an idea of the acceptable conditions. This is tipically a personal evauation because the repairs or restoring are done on your own are cost effective
and could be a reason of enjoyment and satisfaction. Otherwise
pay a professional could be very costly.
A strenght focus on "healthy", complete and preserved bikes is always better because it is easier to respect the originality and a bad surprises due to hidden problems are the most of the times avoided.
Below you can see two extrema year 1994 in different conditions:
In the first case a restoration ensures that you get a nice bike, affordable, original in all the details; the second requires a complete disassembly, the searching the missing parts, documetation for restoration, a lot of work. In this case the cost grouw up, sumtimes "explode", and the time to complete the bike is uncertain.
Accomplice the interest of some media and the steady increase in demand, it has come to create a market with rising prices, especially in Italy. For this reason, unfortunately, sometimes you come across during the research phase and purchase, a lot of sellers overestimate their bikes in comparison with the conditions. Buy an Extrema may run the risk of spending even a few thousand euro a total restorations is needed, moreover if you need siruius professionals. This aspect will be discussed further in the area dedicated to the restoration, but just thinking about tires, painting and stickers, MOT, etc. the total amount could exceed € 2,000. It's hard to find the right bike at the right price, the few true "bargains of the century" are often "under assault", but with a little patience and a trained eye you can found beautiful motorcycles that will show themselves as affordable and nice.
The bikes heavily restored/fully rebuilded are often offered at high prices, often excessive, because the sellers try to "recover costs" and you usually can find two kind of problem: there is no documentation of the restoration which often is only a repair made in a cheap way and the bike loose the value of conservation that is always and for all historic vehicles preferable.
Always bear in mind that a vehicle has and keep its historical value, and also economic one, if well preserved or restored properly and with documents that comprove the work done. I consider "vintage bikes" only those that has these requirements: the others are used motorbike or, in extreme cases, scrap.
The full-fairing bikes could seem perfect, but also can hide some surprise: repair of cracks, rust/oxidation, bad and cheap reparations. On Extrema you can simply lift the tank to recognize some of these problems, but not at all. The good intention or not of the seller, unfortunately, is not easy to prove, so first of all "study" the person and the bike and keep under observation for some time the ads for sale (learn to figure out who you want to avoid) and feel free to do questions and get clear answers from sellers.
You can meet an enthusiast offering a nice preserved bike and/or with good morks done and with documentation that sells a bike maybe for loss of interest or necessity: in this case will be difficult to make a "bargain of the century" thinking only to the money, but you could buy a high value, true and nice bike at a reasonable price. You will be happy because there will be no extra costs. Buy well is the first right step of the "relationship" with your bike.
Unfortunately, in some other cases, there is also speculation by some kind of not-true-motorcycle-enthusiast who is buying up and selling veichles only for money and that is sly. Works are not done properly, but the bike seems nice, it seems original and it is a reassembled in a non-professional and documented way. I find it regrettable from the point of view of the enthusiasts, definitely wrong if we think competition is done to serious professionals who have overhead costs and onerous tax obligations.
Obviously SP versions normally have had a troubled life, so it will be really very difficult to find bikes in very good conditions and complete. Always make the necessary checks on the typical components of the SP bikes because it is not unusual to find motorcycle reassembled, maybe with the right cylinder and carburetor without all the other features. It is necessary to study the features of these models to understand the specificity to make an informed purchase. The SP have higher ratings of standard versions due to their even more difficult to find and to some technical equipment, in addition to the orientation of some collector, but it is the buyer right to claim information and decide if overpay a reassembled bike without the right guarantees and that, at the end, has an historical value that in my opinion is less than any other standard version.
The site would also help spread information to buyers and sellers: If information are available, clear, correct and verified you can better decide how spend your money and what to explain to the seller. Otherwise a seller may demonstrate the value of his bike.