Good questions. My numbers were rough but here is a link that shows dividend-buyback equivalence with full calculations:
https://www.mckinsey.com/capabiliti...rchases-and-dividends-which-create-more-value
Regarding the tax efficiency, I said that basically for two reasons: dividends can/could sometimes be taxed at higher rates than simply selling an appreciated stock that's taxed at long term capital gains rates. I believe this reason is not as significant as it used to be since most/all of your holdings in US-based companies can now be considered "qualified dividends" which are taxed at lower rates than ordinary income (prior treatment of dividend income) and are comparable to LTCG tax rates. Most importantly to me, you have a choice. If you hold a stock from a company paying a dividend you receive the dividend and owe taxes on it. You have no choice. In a situation where a company returns cash to shareholders via buyback you can make that choice for yourself - sell a portion of your holdings into the market and realize gains on those sales or simply hold your stock and see your % ownership of the company increase over time.
I'm certainly not saying all buybacks are good corporate financial decisions, I just don't think it constitutes market manipulation. If the companies are telling you how profitable they are by the financials being public, telling you roughly how much they're buying back, etc then everyone has the information they need to make the right choices for themselves. No one is being deceived. Both buyback and dividend policies can be horrible decisions but that's all dependent on the company's situation and outlook.