The obvious answer is that '2.283.00 - 5.331.00' is not something that can be converted to a float. It expects a format like '1.23'.
First of all it's a range, so you need to split that into two numbers on ' - '.
prices = soup.find(id="priceblock_ourprice").get_text().split(' - ')
Then replace the thousand separator ',' with '' on each price with:
price.replace('?xa0' , '').replace(',', '')
The better option might be to import locale and convert each of the prices (without the currency symbol) with locale.atof().
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