Why is the cost of Turbo Tax Personal and Business On-line so expensive?

There is no such version called "TurboTax Personal & Business On-line". The online version is called "TurboTax Self-Employed" (unless they changed the name for 2019 and haven't informed the masses yet.)  That version is on line.

What you're purchasing in the store is the CD/Desktop version called "TurboTax Home & Business". Functionally, it is the same as the online vresion called "Self-Employed". But the CD version is physically installed on your computer, where as the self-employed version is "on line" and nothing is installed on your computer.

So while functionality between the online version and the CD version is the same, they are not "the same".  But there are other differences that matter.

With the online version, you pay for each individual tax return that is prepared and filed. You also have to create a physically separate online account for each tax return. Additionally, the "forms mode" is not possible with the online version. This can be (or more accurately, *is*) frustrating when you're trying to "follow the money" to see why the online program did whatever it did to come up with a dollar figure and you don't understand why or how.

If you have more than one tax return to file, the online version will be "significantly" more costly. You will pay for each individual federal tax return that you file, weather you e-file or print and mail it to the IRS. additionally, you will pay for each state program that you may need, and they you will pay to file that state return; again, it doesn't matter if you e-file the state return or print and mail it to the state. For some, the online version get's expensive fast.

With the CD version, if you purhcase the CD that comes with "one free state" (not all do) that's significatly cheaper than the online version. With the CD version you physically install it on your computer. Then you can prepare and file as many federal returns as you want. There's no limit. However, the IRS (not TurboTax) does have a limit on how many federal returns you can e-file under the same e-mail address. That maximum is 5. After the 5th federal return is e-filed, any after that have to be printed, signed and mailed to the IRS.  FOr the federal return, there is no additional charge (beyond what you paid for the CD) to e-file or mail the federal return.

The "one free state" means that you don't pay the purchase price of the first state module you download. But depending on the state, you will pay to e-file that state return. You can avoid that charge by electing to print, sign and mail the state return.

For additional states you will pay to purchase that state module. Then you will pay again to e-file that state. But as before, the e-filing charge can be avoided if you elect to print, sign and mail the state return to the state.

Finally, understand that this is a public user-to-user forum and nobody here has any say or control over pricing. Additionally, TurboTax has no control over what 3rd party vendors, (such as Cosco) may charge for the CD.