Alternatives to relay/contactors in DC circuits
If you use a solid state relay you can just step down the voltage with a couple of resistor since the input current might be low enough. Just read the spec of your favorite SSR and size the resistors accordingly. If the maximum input current is \$I_{max}\$ and the minimum on voltage on the input is \$V_{IH}\$ then you want that even when \$I_{max}\$ is flowing in the relay there is ate least \$V_{IH}\$ as its input.

This approach might work but you are dissipating power, that might not be acceptable. The DCDC seems like an overkill to me, a couple of transistor are enough to translate a voltage. The 60Vdc relay might be a good choice but I bet they cost more and they dissipate quite a lot of power too... Search for the SSR that you need based on the contacts specification, i.e. maximum load current/voltage and minimum load voltage, and then see if there's something that consumes less than 50mA on the input, where 50mA is a rough estimate of what you can reasonably obtain with a couple of resistors.