When you sell ~50% of shares in a company for €60k, you implicitly value the total company (100% of shares) at €120k. Your tax office will also most likely (at least in my country) use that transaction to establish a fair (market) valuation.
Of course, you can structure a deal to include discounts, but you have to be careful with that too.
A new investor in one year might scoop in and say "Well, last time your shares were valued at price x, why would I pay substantially more?".
One valuation method for startups is price to revenue, given that their costs are heavily fixed/low cost of replicating the goods you're selling. I think it's much more appropriate especially for early stage startups because they virtually never make money.