I encountered this with H&R block when I had a particularly complex tax situation a few years back (had worked as a contractor for several corporate entities and also had the tail end of full time work plus investment income). H&R block quoted me 3-4 rates, insisting I pay them more money at each step to finish the process.
I realize it's hard because the number of complications that can come up in filing taxes is difficult to enumerate and customers may not know their exact status.... Even so, I'd say the current setup that these companies use is very scammy and unethical.
If your taxes are complex enough to warrant having a tax preparer handle them for you, I recommend avoiding H&R Block. Instead, ask your colleagues, friends, and family for recommendations for an independent tax preparer rather than a chain.
I realize it's hard because the number of complications that can come up in filing taxes is difficult to enumerate and customers may not know their exact status.... Even so, I'd say the current setup that these companies use is very scammy and unethical.