DHL, DHL Express and Deutsche Post are basically the same company and the usage of the brands have some overlap. But to clear up a bit:
- Deutsche Post: Letters and large letters ("Maxibrief"). I think the heaviest thing you can ship with Deutsche Post is 1000 g
- DHL: Standard parcel (all insured to at least 500 €, pricing starts at 6 €), and Päckchen (a small uninsured parcel w/o tracking for up to 2 kg, I think it costs around 3.50 € (*)). Also some special stuff. Largest thing you can ship is something like 32 kilos. DHL parcel inside Germany usually arrive at the next work day or the one after that.
- DHL Express: essentially like UPS, premium carrier. Fast and expensive.
(*) I only lost one parcel, ever, and it was a Päckchen. OTOH I am very sure that it was fraud by the buyer. I never shipped anything as a Päckchen ever since in a commercial context (stuff sold, RMA, ...).
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I can confirm that the German used test & measurement market is completely busted. This - AFAIK - originates from a German law (ElektroG) that makes it cheaper and simpler for companies to recycle/shred surplus equipment than to sell it, thus leading to a small market. You have a very hard time to find anything more recent than early nineties, except for common stuff like DMMs, scopes etc.. The prices are very high, even in auctions. 150-200 € (~200-300 USD) for an analog(!) function generator in the "few MHz"-range is rather common. Everything with a name like "HP", "Racal Dana", "Keithley" on it sells for a lot of money. Even the switch controllers, which I conceive as a benchmark for low-end dirt-cheap T&M gear, sells for quite some money (>60 € ~ >80 USD, much more in some cases).
It is usually a lot cheaper to buy elsewhere, e.g. in Belgium, Netherlands, France, Italy, sometimes UK. Shipping costs are in the 30 € range for these countries, but the prices are a lot better. You can get a decent DDS function gen for under 200 € in these countries (shipping to Germany included).
I bought some stuff in the US, for example: My HP 3478A. With shipping, taxes etc. it cost me around 130 € (calibrated). IIRC half of the price was shipping and taxes, the actual item was 99 $ I think.
In Germany a working, calibrated 3478A sells for something like 200 € upwards.
And don't even get me started about the commercial dealers in Germany. Helmut Singer, Rosenkranz et al have horrid prices. You don't even want to take a look. However, taking a look may be of advantage ... in very rare cases. I bought my 3581A at Singer for 50 € (as-is, untested, missing knobs). Repair was trivial, ex-Bundeswehr stock, well maintained, often calibrated. I guess they took some minor parts and knobs to repair another unit. HOWEVER: I have never seen any offer like this since then at any of the commercial dealers. And I didn't ever seen one before. I attribute this single instance to one-off luck.
There are some (rare) flea markets in Germany where you can get sometimes a good deal. But you're really going to have a hard time getting a good deal online. In some cities there are small gear traders who usually have better prices, too, but their stuff is usually ancient.
tl;dr: don't buy used T&M stuff in Germany. Except if you are walking around in Germany and know the flea markets. Then you might get a good deal.
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Buying T&M internationally
There are some sellers that are well-known to sell "doesn't power up" equipment which is barely more than the case, a few knobs and connectors, stripped of everything of worth. Read the ratings, including positive ones. Sometimes they go like "Yeah, well, it's according to the description, but it's really just an empty box". Don't buy anything from those. Except if you collect HP cases. Then buy from those as much as you can.
Always mind the taxes. If you're in the EU you can just add item value + shipping costs and multiply by 1.2-1.3 and you're usually very close to the final price (except for those where no tax applies).
Don't. ever. buy. via. eBay's global shipping programme. It's nothing more than a rip-off. Shipping internationally and handling the import yourself is more reliable and a lot more cheaper. If you have some excellent offer, but the seller won't ship internationally you can use a mail forwarding service. It's still cheaper than GSP. And, at least the last time I used the GSP, I didn't even get the correct papers. And the package was not cleared by customs. I think that says just about everything you have to know about GSP. They're neither easier, nor cheaper nor faster nor ANYTHING better than doing it yourself.
Example: Last time I bought something via GSP they charged me 80 $ import taxes + fees. The package wouldn't been subject to import tax (only import sales tax, whole different thing. the import salex tax usually dominates, it's 19 % on top of (item price + shipping costs) * import tax). And naturally I would not have had to pay any fees at all for a normal import. I don't know if all EU countries do it like this, but in Germany customs do not impose extra handling fees. If you do it correctly (e.g. you fill out the correct forms with the correct numbers, send it to your mail forwarder, which prints out the forms and puts them on your package) you don't even need to leave the warmth of your house to import something. If you didn't you need to get to your customs office, bring the filled out form or fill it out there, pay the taxes and take your package with you. It's that easy.
With some experience you can handle an import in a few minutes, and it's all legal and ironclad. Which the GSP does not seem to be, given that you neither get the correct papers nor a customs-cleared-sticker on your package with the GSP. Actually I think they just take all the money and hope it slips trough customs (which like 95 % of all parcel does, by the way).