Are the middle perakim of Bava Basra relevent today?

IMHO, the answer is no. Perakim 4-7 of Bava Basra (which Daf Yomi has been learning) deal with the sale of various categories of things, describing what is included and what is not. The common denominator seems to be that these are solely based on the accepted business practice during the time of Chazal and what people expect to get when they consumate a deal. Even the various disputes between the tannaim and amoraim seem to revolve around what people expect to receive or what did they mean when they said they were buying x. There are few to no Torah based sources (e.g. pesukim) for any of these.

Here is a general outline of the perakim.

Perek 4 - Hamocher es habayis discusses what is sold when you sell real property (houses, bathhouses, courtyards, fields, etc.) and what is not, for example when you sell a house the Mishna states that you include teh door but not the key
Perek 5 - Hamocher es hasefina discusses the sale of movable objects, again detailing what is included in the sale and what is not (boats, wagons, animals, etc.)
Perek 6 - Hamocher peiros lachaveiro discusses the sale of agricultural products. It details how much spoilage/wastage there can be in grain and wine etc. It also discusses selling land to build things on it like a house, graves, how much land is given, what access etc.
Perek 7 - Deals with sales of real property how exact do the dimensions need to be.

Given the above, are these at all relevant today? A house buyer in 2017 clearly has very different expectations as to what he is buying in comparison to the times of Chazal as does someone buying wine, a field, a boat, etc. The same goes for every one of these categories.  This seems to be a case of the Talmud simply codifying the accepted business practices at that time which would make it completely irrelevant nowadays.

If I am correct, then we can go one step further. Why bother learning it? Why should I care in 2017 that someone who sold a house in the year 180 sold the door but not the key? What can I learn from this that relates to life today? Of course, you can ask this about a lot of Gemara's, but the difference seems to be that those are at least based on pesukim in Chumash. For example, the distinctions in damages between Keren and Shen Varegel is based on pesukim and therefore never changes. However, these dinim in Bava Basra seem to be solely based on the business practices of the time and are therefore irrelevant today.