Hello,
The sound of the acoustic accordion depends on its manufacture (Italian, German, etc.) and the number of registers it has.
The sound of the piano accordion seems to my ear to be deeper, it is less practical for the performance of triplets for example.
For jazz and gypsy music the sound is more suitable.
I learned on a button piano at the age of 6 years and at the same time the piano (classical). Having two acoustic accordions Fratelli Crosio and Mengascini plus a digital Roland FR3, the three buttons, I had some difficulties at the beginning to get used to the digital, response and touch of the buttons, bellows.
To answer the question about the cost of an accordion, new acoustic ones are very expensive in the big Italian brands (4.000 euros) for an instrument with register. You can find used ones in good condition at specialized dealers, count from 1.500 euros to ..... I can give you some addresses according to your region.
For the digital, Roland dominates the market with models like the FR1 and FR3, the FR7 or FR8 models are now much more expensive and are reserved for accomplished musicians if you want to enjoy all the possibilities.
Then there are the big brands making acoustic/digital guitars, but here we are entering into much bigger budgets.
If you have any other questions don`t hesitate.
Have a nice sunday