Although the sensei/sifu wants to teach it is the student who must prove themselves to them and put in the work, the teacher owes the student nothing. It is the responsibility of the student to learn customs and the way to behave. Without showing a good example of trying to learn the basics and getting stuck in there is no reason why the teacher would want continue to waste time with the student.(Paul B)

If you consider your breathing, it happens all by itself. You do not breath. You are breathed. The breath emerges spontaneously. You do not need to think about it, control it, force it or change it. The process is involuntary and unconscious. When you practice taijiquan, it is very important not to interfere with the natural working of the body. Your breath should be allowed to do as it likes.

90 minutes

Dr Michael Greger (author of How Not To Die) recommends 90 minutes of moderate-intensity exercise every day.

The three doctors who wrote The Okinawa Program maintain that tai chi - with its ancient origins and incredible health benefits - is the ideal form of exercise for modern people. 
If this sounds like a lot of exercise, why not chop it up into smaller increments spaced throughout the day? How many people watch 90 minutes of TV every day?
 

As you like it

Taijiquan students who continue training long term tend to work at a pace that suits their own personality.
They may have lofty aspirations/ambitions, but these are tempered by the reality of who they are and how committed they are. This is quite a Taoist way of being. 

Sport

Sports can be significantly more expensive than martial arts training. And sometimes cheaper too. How much does the clothing cost? Gym membership? A season ticket?
As with all things, the cost of something is relative to what you think is appropriate and what you are prepared/willing to pay...

Tai chi is often described as "meditation in motion," but it might well be called "medication in motion." There is growing evidence that this mind-body practice, which originated in China as a martial art, has value in treating or preventing many health problems. And you can get started even if you aren't in top shape or the best of health.

Tai chi differs from other types of exercise in several respects. The movements are usually circular and never forced, the muscles are relaxed rather than tensed, the joints are not fully extended or bent, and connective tissues are not stretched. Tai chi addresses the key components of fitness — muscle strength, flexibility, balance, and, to a lesser degree, aerobic conditioning.
(Harvard Medical School’s Harvard Health Publication, May 2009)

Tai chi is the one exercise that can universally help solve our growing health crisis. It has stood the test of thousands of years. We have a generation of baby boomers with increasing health problems; old people who are sick, in pain, fearful, and cranky; a middle class that is increasingly incapable of affording most of the drugs that are prescribed for their ailments; children that are flaccid, diabetic and asthmatic. People of all ages are addicted to drugs, alcohol, sugar, cigarettes, and caffeine. Stress follows almost everyone like a shadow. 
(Bruce Frantzis)

Motor learning

For many people, their fitness regime does not take into account 'motor learning'.

Motor learning is about the process of using the body, rather than simply exercising the body.

Agility, mobility, relaxed spontaneous movement, balance, structure, alignment, biomechanics, efficiency, ambidextrous body use, joint health, coordination, skill, emotional wellbeing or psychological flexibility.

Tai chi combines exercise with motor learning.

Imagine waking up each morning full of energy and vitality yet also feeling calm and relaxed about the day to come. It sounds like a miracle yet this state of abundant health and wellbeing should be our birthright. In our natural state we would face each day with joy, peace, and a deep connection with our bodies.

(Jane Alexander)