Creeping communism in a market economy

In a higher phase of communist society, after the enslaving subordination of the individual to the division of labor, and therewith also the antithesis between mental and physical labor, has vanished; after labor has become not only a means of life but life's prime want; after the productive forces have also increased with the all-around development of the individual, and all the springs of co-operative wealth flow more abundantly—only then can the narrow horizon of bourgeois right be crossed in its entirety and society inscribe on its banners: From each according to his ability, to each according to his needs!

Every once in a while, I see little hints of the above dynamic in our capitalist society. Basically, it occurs when a person has so much money that he thinks nothing of parting with it. I've wondered how this plays out with waiters -- their wages are typically lower than is typical for such work, and it is supplemented by tips. As my income has increased over the years, I have increasingly left "large" tips -- tips that exceed the standard percentage, but which are still very affordable to me. I've wondered how this would play out when taken to extremes --could we reach a point where payment for services was essentially voluntary (from each according to his ability)?

I'll continue with the above thought; but first, it appears that "pay what you want" has caught on in a more extensive manner. Panera has introduced a meal that is funded totally by donations. So far, they say it is sustainable.

Of course, we have to assume that Panera is driven purely by profit; but it does say something about the development of our society that this business model is plausible. I like it much better than the model where the seller gives a portion of their profits to charity -- the "pay what you want" model cuts out the middle man and uses the business' own economy of scale to facilitate the charity (rather than relying on an outside organization), and it also offers much more flexibility in terms of how much a person wants to contribute or take. Perhaps most importantly, it doesn't distinguish between the granter and recipient of charity; they are both just people going about their lives and acquiring their dinner in the same way.

That being said, I don't want to be naive. Both the "pay as you go" system and the over-tipping strategy can have unintended consequences. They can even be cynically manipulated. 

First: over-tipping. Waiters know which customers are likely to leave a large tip, and I expect that they provide more attention to those customers in the hopes of securing a larger tip. This could lead to the perverse scenario where people are provided services according to stereotypes rather than their own willingness to pay for service. That may actually be a step backwards. Furthermore, the erratic nature of tips could make it difficult for potential waiters to decide which job to take; over-tipping could actually make low-wage workers less secure economically (if it becomes linked to lower wages for workers who receive tips).

Second: "pay what you want". I assume that Panera wants to attract people who are ready to part with large amounts of money, and will spend some of their money on other products that Panera offers (and tips for the staff). So this model could not cover the expenses of the entire store. We also have to trust that Panera is not pocketing the excess donations. Finally, Panera could manipulate the system to minimize the number of meals that they provide without full payment. For instance, they can place stores in locations that are only accessible to wealthy people. They could even lobby for laws that drive indigent people out of retail districts (such as "Measure S", which was narrowly defeated in Berkeley, CA).

Given the above considerations, I think that the first thing I will look for in any proto-communist retail establishment is that they have publicly accessible bathrooms. That is the simplest implementation of "each according to his need".