Prices vary quite a bit at times between Europe and USA. So don't always assume the Euro price is equivalent to the price in the U.S.
The early 280SL cylinder head, part number 130-010-26-20, (old part number 130-010-19-20) is still available, and it lists in the U.S. for $4,490, wholesales for $3,100.
The late 280SL cylinder head, part number 130-010-18-21, is still available. It lists in the U.S. for $3,540, and wholesales for $2,490.
For those of you that want to check the availability of a part always use this Classic Center website link:
https://partssearch.mercedes-benz-classic.com/ You Must type in the letter "A" before the part number. No spaces or dashes. If there is a star beside the price (in Euros) that means the part is on clearance, and that once it's out of stock that'll be the end of that part.....forever. If it's a new production number it'll have the a "NEW" icon next to price. If you're searching for a DIN number you much put an "N" in front of the number. Though, bear in mind that not all DIN numbers will come up in Classic.
Now, after you have confirmed availability on the Classic website, and you live in the U.S., you can go so any online Mercedes dealer website. Type in the part number (without spaces or dashes) and it'll tell you the price here in the U.S.....what it retails for and what wholesale cost is. If any place charges you more than retail then run like hell from those places. This is the website store I use for U.S. pricing:
https://www.mercedesbenzpartscenter.com/ There are many others like this, but this one has the best pricing that I can find.
I've struggled many years when someone wants a quote because Mercedes does not allow independents to have access to any type of pricing database. So I have to make up a list of part numbers, send it to my parts fella at a dealership, he then has to type each number in manually to make up the quote, and then he has to send that to me. It's a royal pain in the A**, but the two aforementioned websites help quite a bit when I want to make up a quote late at night in my home.